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CX2SA > SATDIG 28.11.20 21:16l 830 Lines 32293 Bytes #999 (0) @ WW
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Today's Topics:
1. Re: Fiberglass Cross-boom Alternative (Jean Marc Momple)
2. Re: Fiberglass Cross-boom Alternative (KENT BRITAIN)
3. Re: Fiberglass Cross-boom Alternative (Jean Marc Momple)
4. Successful PSAT SSTV and Waterfall Drawing Experiment
(Stephen DeVience)
5. Re: Fiberglass Cross-boom Alternative (KENT BRITAIN)
6. Icom 910H for sale. (tjschuessler@???????.????
7. other used gear. (tjschuessler@???????.????
----------------------------------------------------------------------
Message: 1
Date: Sat, 28 Nov 2020 20:27:51 +0400
From: Jean Marc Momple <jean.marc.momple@?????.???>
To: KENT BRITAIN <wa5vjb@?????.???>
Cc: "amsat-bb@?????.???? <amsat-bb@?????.???>
Subject: Re: [amsat-bb] Fiberglass Cross-boom Alternative
Message-ID: <9757B7BB-7CE7-4B7B-8522-8E5B77F7E43F@?????.???>
Content-Type: text/plain; charset=utf-8
Kent,
Thanks, good tips for antenna builders.
But it all boils down to what one wish to do with the antenna, as far as
LEO?s are concerned getting the max from a Yagi antenna is not that
important. So Tony does not have to worry to much about the boom.
I agree with your observations and also about Mr LFA claims, as I studied
his designs and build a few and found also many flaws that he tends to
minimise. However to his credit it is a superb antenna concept.
My philosophy is to avoid (as much as practically possible) any metallic
object except the elements as far as possible which makes the design as
close as possible to the existing models prediction. Actually I am building
a 3M dish and the feed support is all fiberglass, using resins and epoxy
glue. Sure the coax or waveguide effect cannot be avoided but taking it at
the end for Yagi's and in the centre for a dish minimise negative effect of
same (which is quite difficult to model or predict, at least for me).
End-mounting is the best for Yagi?s and I am presently building an array for
70cm (inspired from the Cal-Poly EME experiments) with this configuration,
but this is not possible for the long VHF LFA I am also building (7m long).
In my opinion it is all compromises and depending on what you want to
achieve within your environment, means, available material in the hardware
and building skills, there is no silver bullet.
But what a fun building your own antennas and get better result than
commercially available ones at much lower cost.
73
Jean Marc (3B8DU)
> On Nov 27, 2020, at 10:26 PM, KENT BRITAIN via AMSAT-BB
<amsat-bb@?????.???> wrote:
>
> Hi Tony:
> Thanks for giving me a topic for my next CQ Antenna Column.
> This topic comes up every few years and also affects the hams who mount
> a vertically polarized Yagi on a vertical mast.
> On the antenna range you quickly see that metal (or even plastics) near
the tip
> of a Yagi element moves it down in frequency. When I have a Yagi on the
> range, I put a small bit of Yagi element on a stick and hold it near each
element
> while watching gain.
> Get the metal near the tip and gain goes up, Element too Short!Get the
metal near the tip and gain goes down. Element too Long!
> This lets you do a quick look at how well the Yagi is working.
> So it is the supporting mast near an element tip that does the
detuning.With a non-conductive mast what do you do with the coax?
> Did you run it back down your fiberglass mast? You just #@??? your
> non-conductive mast with a conductor.
> Yes, I did measure a few tenths of a dB degradation, but the alternative
> is a long loop of coax out the back of the antenna. How much loss do
> you think is in that loop?
> So mounting the Crossed Yagi so that both sets of elements are 45 deg to
> the mast and midway between element sets is the 2nd best solution.
> Best solution would of course be end mounting. But that his it's own
> problems if you have a lot of elements! Coax can be run back along the
> Yagi boom and along the mast with no measurable effects.
>
> Also extend the mast just enough for the antenna clamp to get a good grip.
> That is, have the mast extend only an inch or so beyond the clamps.
>
> Yes, had an interesting talk with Mr. LFA at Dayton several years ago.
> I pointed out that the antenna he had on display could NOT have produced
> that polar plot! He was simplifying his model to get a cleaner plot. .
>
> Kent WA5VJB/2E0VAA/G8EMY
> PS As an FYI don't think the solution is a Carbon Fiber boom. At
Microwave Update I demonstrated a 915 MHz Yagi made using
> Carbon Fiber Rod for the elements. Gain about the same as Aluminum.
> Another FYI. Voyager 1 and 2 use a 10 foot Carbon Fiber parabolic
dish antenna. They took the antennas out on the antenna range and they
meet specification. As a weight saving they were NOT metalized.
>
>
>
> Subject: Re: [amsat-bb] Fiberglass Cross-boom Alternative?
> To: Tony <73guddx@?????.???>, AMSAT-BB@?????.??? <AMSAT-BB@?????.???>
>
>
> Don't dismiss using a metal cross-boom. People say it won't work without
actually examining the problem. When antenna guru Kent Britain, WA5VJB
looked at the problem he found a metal boom to work quite well. He then
tested it on the antenna range and verified it worked. You can see the
paper he presented at an AMSAT symposium here:
> Using Metal Cross Booms w/ Satellite Antennas
>
> When I had a permanent satellite station I used a metal cross-boom, and
there were several others in the OSCAR-13 and AO-40 era that did.
>
> 73,
> Gary "Joe", kk0sd
>
> -----Original Message-----
> From: AMSAT-BB <amsat-bb-bounces@?????.???> On Behalf Of Tony via AMSAT-BB
> Sent: Tuesday, November 24, 2020 6:00 PM
> To: AMSAT-BB <amsat-bb@?????.???>
> Subject: [amsat-bb] Fiberglass Cross-boom Alternative?
>
> All:
>
> Is there a cheaper non-metallic alternative to fiberglass cross booms?
> Or maybe a wholesale fiberglass rod distributor that has such a beast at a
reasonable price?
>
> Tony -K2MO
> |
> |
> | |
> Using Metal Cross Booms w/ Satellite Antennas
>
>
> |
>
> |
>
> |
>
>
>
> _______________________________________________
> Sent via AMSAT-BB@?????.???. AMSAT-NA makes this open forum available
> to all interested persons worldwide without requiring membership. Opinions
expressed
> are solely those of the author, and do not reflect the official views of
AMSAT-NA.
> Not an AMSAT-NA member? Join now to support the amateur satellite program!
> Subscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb
------------------------------
Message: 2
Date: Sat, 28 Nov 2020 17:05:55 +0000 (UTC)
From: KENT BRITAIN <wa5vjb@?????.???>
To: Jean Marc Momple <jean.marc.momple@?????.???>
Cc: "amsat-bb@?????.???? <amsat-bb@?????.???>
Subject: Re: [amsat-bb] Fiberglass Cross-boom Alternative
Message-ID: <2058569228.2350217.1606583155618@????.?????.???>
Content-Type: text/plain; charset=UTF-8
The problem is anything near the element changes it's resonate
frequency.Even plastics.??? That's why I prefer actual measurements.
The software programs are very useful, but I rarely publish a design I have
not
built and tested on the antenna range.?? Tooooo many holes in those
simulations program.
So far we have found 3 families of antennas that even HFSS cannot
simulate.Oh you run them though HFSS but the results do not come even close
to antennarange findings.
Did learn an interesting technique this week.Would you like to build a 20
element Yagi for 160 Meters on a boom about 20 mm long?After you finish
construction just put it in a Bose-Einstein condensate.
73 Kent WA5VJB
On Saturday, November 28, 2020, 10:41:45 AM CST, Jean Marc Momple
<jean.marc.momple@?????.???> wrote:
Kent,
Thanks, good tips for antenna builders.
But it all boils down to what one wish to do with the antenna, as far as
LEO?s are concerned getting the max from a Yagi antenna is not that
important. So Tony does not have to worry to much about the boom.
I agree with your observations and also about Mr LFA claims, as I studied
his designs and build a few and found also many flaws that he tends to
minimise. However to his credit it is a superb antenna concept.
My philosophy is to avoid (as much as practically possible) any metallic
object except the elements as far as possible which makes the design as
close as possible to the existing models prediction. Actually I am building
a 3M dish and the feed support is all fiberglass, using resins and epoxy
glue. Sure the coax or waveguide effect cannot be avoided but taking it at
the end for Yagi's and in the centre for a dish minimise negative effect of
same (which is quite difficult to model or predict, at least for me).
End-mounting is the best for Yagi?s and I am presently building an array for
70cm (inspired from the Cal-Poly EME experiments) with this configuration,
but this is not possible for the long VHF LFA I am also building (7m long).
In my opinion it is all compromises and depending on what you want to
achieve within your environment, means, available material in the hardware
and building skills, there is no silver bullet.
But what a fun building your own antennas and get better result than
commercially available ones at much lower cost.
73
Jean Marc (3B8DU)
> On Nov 27, 2020, at 10:26 PM, KENT BRITAIN via AMSAT-BB
<amsat-bb@?????.???> wrote:
>
> Hi Tony:
> Thanks for giving me a topic for my next CQ Antenna Column.
> This topic comes up every few years and also affects the hams who mount?
> a vertically polarized Yagi on a vertical mast.
> On the antenna range you quickly see that metal (or even plastics) near
the tip
> of a Yagi element moves it down in frequency.? When I have a Yagi on the
> range, I put a small bit of Yagi element on a stick and hold it near each
element
> while watching gain.? ?
> Get the metal near the tip and gain goes up,? Element too Short!Get the
metal near the tip and gain goes down.? Element too Long!
> This lets you do a quick look at how well the Yagi is working.
> So it is the supporting mast near an element tip that does the
detuning.With a non-conductive mast what do you do with the coax??
> Did you run it back down your fiberglass mast?? ? You just? #@??? your?
> non-conductive mast with a conductor.
> Yes, I did measure a few tenths of a dB degradation, but the alternative
> is a long loop of coax out the back of the antenna.? How much loss do?
> you think is in that loop?
> So mounting the Crossed Yagi so that both sets of elements are 45 deg to?
> the mast and midway between element sets is the 2nd best solution.?
> Best solution would of course be end mounting.? But that his it's own?
> problems if you have a lot of elements!? ? Coax can be run back along the?
> Yagi boom and along the mast with no measurable effects.?
>
> Also extend the mast just enough for the antenna clamp to get a good grip.?
> That is, have the mast extend only an inch or so beyond the clamps.?
>
> Yes, had an interesting talk with Mr. LFA at Dayton several years ago.?
> I pointed out that the antenna he had on display could NOT have produced
> that polar plot!? He was simplifying his model to get a cleaner plot.? .?
>
> Kent? WA5VJB/2E0VAA/G8EMY
> PS? As an FYI don't think the solution is a Carbon Fiber boom.? ? ? At
Microwave Update I demonstrated a 915 MHz Yagi made using
>? ? ? Carbon Fiber Rod for the elements.? Gain about the same as Aluminum.?
>? ? ? Another FYI.? Voyager 1 and 2 use a 10 foot Carbon Fiber parabolic
dish antenna.? ? ? They took the antennas out on the antenna range and they
meet specification.? ? ? As a weight saving they were NOT metalized.?
>? ? ? ?
>
>
> Subject: Re: [amsat-bb] Fiberglass Cross-boom Alternative?
> To: Tony <73guddx@?????.???>, AMSAT-BB@?????.??? <AMSAT-BB@?????.???>
>
>
> Don't dismiss using a metal cross-boom. People say it won't work without
actually examining the problem. When antenna guru Kent Britain, WA5VJB
looked at the problem he found a metal boom to work quite well. He then
tested it on the antenna range and verified it worked.? You can see the
paper he presented at an AMSAT symposium here:
> Using Metal Cross Booms w/ Satellite Antennas
>
> When I had a permanent satellite station I used a metal cross-boom, and
there were several others in the OSCAR-13 and AO-40 era that did.
>
> 73,
> Gary "Joe", kk0sd
>
> -----Original Message-----
> From: AMSAT-BB <amsat-bb-bounces@?????.???> On Behalf Of Tony via AMSAT-BB
> Sent: Tuesday, November 24, 2020 6:00 PM
> To: AMSAT-BB <amsat-bb@?????.???>
> Subject: [amsat-bb] Fiberglass Cross-boom Alternative?
>
> All:
>
> Is there a cheaper non-metallic alternative to fiberglass cross booms?
> Or maybe a wholesale fiberglass rod distributor that has such a beast at a
reasonable price?
>
> Tony -K2MO
> |
> |
> |? |
> Using Metal Cross Booms w/ Satellite Antennas
>
>
> |
>
> |
>
> |
>
>
>
> _______________________________________________
> Sent via AMSAT-BB@?????.???. AMSAT-NA makes this open forum available
> to all interested persons worldwide without requiring membership. Opinions
expressed
> are solely those of the author, and do not reflect the official views of
AMSAT-NA.
> Not an AMSAT-NA member? Join now to support the amateur satellite program!
> Subscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb
------------------------------
Message: 3
Date: Sat, 28 Nov 2020 21:26:34 +0400
From: Jean Marc Momple <jean.marc.momple@?????.???>
To: KENT BRITAIN <wa5vjb@?????.???>
Cc: "amsat-bb@?????.???? <amsat-bb@?????.???>
Subject: Re: [amsat-bb] Fiberglass Cross-boom Alternative
Message-ID: <2D63CEF2-8649-4EA4-9B21-9FF32C5AB348@?????.???>
Content-Type: text/plain; charset=utf-8
Kent,
Tend to agree, this is why RF is still an art and whatever professional
antenna designers may say (I am a ex mobile telecom executive and somehow
know what I am speaking about) and HAM?s may still do some breakthrough in
this fields as we may experiment many things on the whole spectrum.
Please share more on your idea about the 160m antenna. But fail to
understand how the Bose-Einstein condensate is applied there, may be you may
enlighten us.
Anyway it just fun and these exchanges bring ideas.
73
Jean Marc (3B8DU)
> On Nov 28, 2020, at 9:05 PM, KENT BRITAIN <wa5vjb@?????.???> wrote:
>
> The problem is anything near the element changes it's resonate frequency.
> Even plastics. That's why I prefer actual measurements.
>
> The software programs are very useful, but I rarely publish a design I
have not
> built and tested on the antenna range. Tooooo many holes in those
simulations program.
>
> So far we have found 3 families of antennas that even HFSS cannot simulate.
> Oh you run them though HFSS but the results do not come even close to
antenna
> range findings.
>
> Did learn an interesting technique this week.
> Would you like to build a 20 element Yagi for 160 Meters on a boom about
20 mm long?
> After you finish construction just put it in a Bose-Einstein condensate.
>
> 73 Kent WA5VJB
>
>
> On Saturday, November 28, 2020, 10:41:45 AM CST, Jean Marc Momple
<jean.marc.momple@?????.???> wrote:
>
>
> Kent,
>
> Thanks, good tips for antenna builders.
>
> But it all boils down to what one wish to do with the antenna, as far as
LEO?s are concerned getting the max from a Yagi antenna is not that
important. So Tony does not have to worry to much about the boom.
>
> I agree with your observations and also about Mr LFA claims, as I studied
his designs and build a few and found also many flaws that he tends to
minimise. However to his credit it is a superb antenna concept.
>
> My philosophy is to avoid (as much as practically possible) any metallic
object except the elements as far as possible which makes the design as
close as possible to the existing models prediction. Actually I am building
a 3M dish and the feed support is all fiberglass, using resins and epoxy
glue. Sure the coax or waveguide effect cannot be avoided but taking it at
the end for Yagi's and in the centre for a dish minimise negative effect of
same (which is quite difficult to model or predict, at least for me).
>
> End-mounting is the best for Yagi?s and I am presently building an array
for 70cm (inspired from the Cal-Poly EME experiments) with this
configuration, but this is not possible for the long VHF LFA I am also
building (7m long).
>
> In my opinion it is all compromises and depending on what you want to
achieve within your environment, means, available material in the hardware
and building skills, there is no silver bullet.
>
> But what a fun building your own antennas and get better result than
commercially available ones at much lower cost.
>
> 73
>
>
> Jean Marc (3B8DU)
>
> > On Nov 27, 2020, at 10:26 PM, KENT BRITAIN via AMSAT-BB
<amsat-bb@?????.??? <mailto:amsat-bb@?????.???>> wrote:
> >
> > Hi Tony:
> > Thanks for giving me a topic for my next CQ Antenna Column.
> > This topic comes up every few years and also affects the hams who mount
> > a vertically polarized Yagi on a vertical mast.
> > On the antenna range you quickly see that metal (or even plastics) near
the tip
> > of a Yagi element moves it down in frequency. When I have a Yagi on the
> > range, I put a small bit of Yagi element on a stick and hold it near
each element
> > while watching gain.
> > Get the metal near the tip and gain goes up, Element too Short!Get the
metal near the tip and gain goes down. Element too Long!
> > This lets you do a quick look at how well the Yagi is working.
> > So it is the supporting mast near an element tip that does the
detuning.With a non-conductive mast what do you do with the coax?
> > Did you run it back down your fiberglass mast? You just #@??? your
> > non-conductive mast with a conductor.
> > Yes, I did measure a few tenths of a dB degradation, but the alternative
> > is a long loop of coax out the back of the antenna. How much loss do
> > you think is in that loop?
> > So mounting the Crossed Yagi so that both sets of elements are 45 deg to
> > the mast and midway between element sets is the 2nd best solution.
> > Best solution would of course be end mounting. But that his it's own
> > problems if you have a lot of elements! Coax can be run back along the
> > Yagi boom and along the mast with no measurable effects.
> >
> > Also extend the mast just enough for the antenna clamp to get a good grip.
> > That is, have the mast extend only an inch or so beyond the clamps.
> >
> > Yes, had an interesting talk with Mr. LFA at Dayton several years ago.
> > I pointed out that the antenna he had on display could NOT have produced
> > that polar plot! He was simplifying his model to get a cleaner plot. .
> >
> > Kent WA5VJB/2E0VAA/G8EMY
> > PS As an FYI don't think the solution is a Carbon Fiber boom. At
Microwave Update I demonstrated a 915 MHz Yagi made using
> > Carbon Fiber Rod for the elements. Gain about the same as Aluminum.
> > Another FYI. Voyager 1 and 2 use a 10 foot Carbon Fiber parabolic
dish antenna. They took the antennas out on the antenna range and they
meet specification. As a weight saving they were NOT metalized.
> >
> >
> >
> > Subject: Re: [amsat-bb] Fiberglass Cross-boom Alternative?
> > To: Tony <73guddx@?????.??? <mailto:73guddx@?????.???>>,
AMSAT-BB@?????.??? <mailto:AMSAT-BB@?????.???> <AMSAT-BB@?????.???
<mailto:AMSAT-BB@?????.???>>
> >
> >
> > Don't dismiss using a metal cross-boom. People say it won't work without
actually examining the problem. When antenna guru Kent Britain, WA5VJB
looked at the problem he found a metal boom to work quite well. He then
tested it on the antenna range and verified it worked. You can see the
paper he presented at an AMSAT symposium here:
> > Using Metal Cross Booms w/ Satellite Antennas
> >
> > When I had a permanent satellite station I used a metal cross-boom, and
there were several others in the OSCAR-13 and AO-40 era that did.
> >
> > 73,
> > Gary "Joe", kk0sd
> >
> > -----Original Message-----
> > From: AMSAT-BB <amsat-bb-bounces@?????.???
<mailto:amsat-bb-bounces@?????.???>> On Behalf Of Tony via AMSAT-BB
> > Sent: Tuesday, November 24, 2020 6:00 PM
> > To: AMSAT-BB <amsat-bb@?????.??? <mailto:amsat-bb@?????.???>>
> > Subject: [amsat-bb] Fiberglass Cross-boom Alternative?
> >
> > All:
> >
> > Is there a cheaper non-metallic alternative to fiberglass cross booms?
> > Or maybe a wholesale fiberglass rod distributor that has such a beast at
a reasonable price?
> >
> > Tony -K2MO
> > |
> > |
> > | |
> > Using Metal Cross Booms w/ Satellite Antennas
> >
> >
> > |
> >
> > |
> >
> > |
> >
> >
> >
> > _______________________________________________
> > Sent via AMSAT-BB@?????.???. <mailto:AMSAT-BB@?????.???.> AMSAT-NA makes
this open forum available
> > to all interested persons worldwide without requiring membership.
Opinions expressed
> > are solely those of the author, and do not reflect the official views of
AMSAT-NA.
> > Not an AMSAT-NA member? Join now to support the amateur satellite program!
> > Subscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb
<https://www.amsat.org/mailman/listinfo/amsat-bb>
------------------------------
Message: 4
Date: Sat, 28 Nov 2020 13:39:50 -0500
From: Stephen DeVience <sjdevience@?????.???>
To: amsat-bb@?????.???
Subject: [amsat-bb] Successful PSAT SSTV and Waterfall Drawing
Experiment
Message-ID:
<CAMPfQQDbv1vTLR-_J9vEegEOW7mEsXZcYHPD=JnvEb3zDTKYdw@????.?????.???>
Content-Type: text/plain; charset="UTF-8"
Adding to Brian's explanation,
For the transmission, I was using a 5W RS-HFIQ radio attached to an RM
Italy amplifier. The radio is run by HDSDR, so I was able to pipe in audio
from both FLDIGI and MMSSTV simultaneously. I continuously sent a blank PSK
tone with FLDIGI and then sent various SSTV images from MMSSTV. I had
Orbitron controlling the HDSDR frequency to correct for uplink doppler, so
both the PSK and SSTV would stay on the correct frequency. It also took a
few tries to calibrate the uplink frequency, which was about 250 Hz lower
than the published value. This was important because SSTV demodulators want
the tones at the correct frequencies.
For spectrum writing, a sent a message with a second instance of FLDIGI
while the first instance was sending PSK.
-Stephen, N8URE
------------------------------
Message: 5
Date: Sat, 28 Nov 2020 18:44:18 +0000 (UTC)
From: KENT BRITAIN <wa5vjb@?????.???>
To: Jean Marc Momple <jean.marc.momple@?????.???>
Cc: "amsat-bb@?????.???? <amsat-bb@?????.???>
Subject: Re: [amsat-bb] Fiberglass Cross-boom Alternative
Message-ID: <1640196076.2344181.1606589058164@????.?????.???>
Content-Type: text/plain; charset=UTF-8
Yes, imagine a 145 MHz antenna build using 100 mm diameter elements.??
We see good gain and very very broad frequency response with extremely good???
Return Loss.?? We are using these in RFID applications where the antenna is
used??
to transmit and receive at the same time.??
NEC does everything as an infinitesimal line.? Change the diameter of the
element, and????
NEC changes the length of the line to compensate for the change in
inductance.???
HFSS doesn't do any better.???? Haven't tried it on any of the Time Domain
programs.???
So far all work has been on network analyzers and the antenna range.
The Bose Condensate is any interesting 'fluid' that only exists a few
thousands of a??
degree above absolute Zero.? It drastically changes the speed of light.
Kent
On Saturday, November 28, 2020, 11:26:41 AM CST, Jean Marc Momple
<jean.marc.momple@?????.???> wrote:
Kent,
Tend to agree, this is why RF is still an art and whatever professional
antenna designers may say (I am a ex mobile telecom executive and somehow
know what I am speaking about) and HAM?s may still do some breakthrough in
this fields as we may experiment many things on the whole spectrum.
Please share more on your idea about the 160m antenna. But fail to
understand how the?Bose-Einstein condensate is applied there, may be you may
enlighten us.
Anyway it just fun and these exchanges bring ideas.
73
Jean Marc (3B8DU)
On Nov 28, 2020, at 9:05 PM, KENT BRITAIN <wa5vjb@?????.???> wrote:
The problem is anything near the element changes it's resonate
frequency.Even plastics.??? That's why I prefer actual measurements.
The software programs are very useful, but I rarely publish a design I have
not
built and tested on the antenna range.?? Tooooo many holes in those
simulations program.
So far we have found 3 families of antennas that even HFSS cannot
simulate.Oh you run them though HFSS but the results do not come even close
to antennarange findings.
Did learn an interesting technique this week.Would you like to build a 20
element Yagi for 160 Meters on a boom about 20 mm long?After you finish
construction just put it in a Bose-Einstein condensate.
73 Kent WA5VJB
On Saturday, November 28, 2020, 10:41:45 AM CST, Jean Marc Momple
<jean.marc.momple@?????.???> wrote:
Kent,
Thanks, good tips for antenna builders.
But it all boils down to what one wish to do with the antenna, as far as
LEO?s are concerned getting the max from a Yagi antenna is not that
important. So Tony does not have to worry to much about the boom.
I agree with your observations and also about Mr LFA claims, as I studied
his designs and build a few and found also many flaws that he tends to
minimise. However to his credit it is a superb antenna concept.
My philosophy is to avoid (as much as practically possible) any metallic
object except the elements as far as possible which makes the design as
close as possible to the existing models prediction. Actually I am building
a 3M dish and the feed support is all fiberglass, using resins and epoxy
glue. Sure the coax or waveguide effect cannot be avoided but taking it at
the end for Yagi's and in the centre for a dish minimise negative effect of
same (which is quite difficult to model or predict, at least for me).
End-mounting is the best for Yagi?s and I am presently building an array for
70cm (inspired from the Cal-Poly EME experiments) with this configuration,
but this is not possible for the long VHF LFA I am also building (7m long).
In my opinion it is all compromises and depending on what you want to
achieve within your environment, means, available material in the hardware
and building skills, there is no silver bullet.
But what a fun building your own antennas and get better result than
commercially available ones at much lower cost.
73
Jean Marc (3B8DU)
> On Nov 27, 2020, at 10:26 PM, KENT BRITAIN via AMSAT-BB
<amsat-bb@?????.???> wrote:
>
> Hi Tony:
> Thanks for giving me a topic for my next CQ Antenna Column.
> This topic comes up every few years and also affects the hams who mount?
> a vertically polarized Yagi on a vertical mast.
> On the antenna range you quickly see that metal (or even plastics) near
the tip
> of a Yagi element moves it down in frequency.? When I have a Yagi on the
> range, I put a small bit of Yagi element on a stick and hold it near each
element
> while watching gain.? ?
> Get the metal near the tip and gain goes up,? Element too Short!Get the
metal near the tip and gain goes down.? Element too Long!
> This lets you do a quick look at how well the Yagi is working.
> So it is the supporting mast near an element tip that does the
detuning.With a non-conductive mast what do you do with the coax??
> Did you run it back down your fiberglass mast?? ? You just? #@??? your?
> non-conductive mast with a conductor.
> Yes, I did measure a few tenths of a dB degradation, but the alternative
> is a long loop of coax out the back of the antenna.? How much loss do?
> you think is in that loop?
> So mounting the Crossed Yagi so that both sets of elements are 45 deg to?
> the mast and midway between element sets is the 2nd best solution.?
> Best solution would of course be end mounting.? But that his it's own?
> problems if you have a lot of elements!? ? Coax can be run back along the?
> Yagi boom and along the mast with no measurable effects.?
>
> Also extend the mast just enough for the antenna clamp to get a good grip.?
> That is, have the mast extend only an inch or so beyond the clamps.?
>
> Yes, had an interesting talk with Mr. LFA at Dayton several years ago.?
> I pointed out that the antenna he had on display could NOT have produced
> that polar plot!? He was simplifying his model to get a cleaner plot.? .?
>
> Kent? WA5VJB/2E0VAA/G8EMY
> PS? As an FYI don't think the solution is a Carbon Fiber boom.? ? ? At
Microwave Update I demonstrated a 915 MHz Yagi made using
>? ? ? Carbon Fiber Rod for the elements.? Gain about the same as Aluminum.?
>? ? ? Another FYI.? Voyager 1 and 2 use a 10 foot Carbon Fiber parabolic
dish antenna.? ? ? They took the antennas out on the antenna range and they
meet specification.? ? ? As a weight saving they were NOT metalized.?
>? ? ? ?
>
>
> Subject: Re: [amsat-bb] Fiberglass Cross-boom Alternative?
> To: Tony <73guddx@?????.???>, AMSAT-BB@?????.??? <AMSAT-BB@?????.???>
>
>
> Don't dismiss using a metal cross-boom. People say it won't work without
actually examining the problem. When antenna guru Kent Britain, WA5VJB
looked at the problem he found a metal boom to work quite well. He then
tested it on the antenna range and verified it worked.? You can see the
paper he presented at an AMSAT symposium here:
> Using Metal Cross Booms w/ Satellite Antennas
>
> When I had a permanent satellite station I used a metal cross-boom, and
there were several others in the OSCAR-13 and AO-40 era that did.
>
> 73,
> Gary "Joe", kk0sd
>
> -----Original Message-----
> From: AMSAT-BB <amsat-bb-bounces@?????.???> On Behalf Of Tony via AMSAT-BB
> Sent: Tuesday, November 24, 2020 6:00 PM
> To: AMSAT-BB <amsat-bb@?????.???>
> Subject: [amsat-bb] Fiberglass Cross-boom Alternative?
>
> All:
>
> Is there a cheaper non-metallic alternative to fiberglass cross booms?
> Or maybe a wholesale fiberglass rod distributor that has such a beast at a
reasonable price?
>
> Tony -K2MO
> |
> |
> |? |
> Using Metal Cross Booms w/ Satellite Antennas
>
>
> |
>
> |
>
> |
>
>
>
> _______________________________________________
> Sent via AMSAT-BB@?????.???. AMSAT-NA makes this open forum available
> to all interested persons worldwide without requiring membership. Opinions
expressed
> are solely those of the author, and do not reflect the official views of
AMSAT-NA.
> Not an AMSAT-NA member? Join now to support the amateur satellite program!
> Subscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb
------------------------------
Message: 6
Date: Sat, 28 Nov 2020 12:51:13 -0600
From: <tjschuessler@???????.???>
To: "'AMSAT BB'" <amsat-bb@?????.???>
Subject: [amsat-bb] Icom 910H for sale.
Message-ID: <02a301d6c5b7$72962d60$57c28820$@???????.???>
Content-Type: text/plain; charset="us-ascii"
I have no dog in the hunt here, but here is a deal on a supposed never used
Icom 910H from Main Trading Company in Paris Texas. Great rig for portable
full duplex satellite use base or portable. At the top of their used gear
list.
https://www.mtcradio.com/u6108-as-new-never-used-icom-ic-910h/
Tom Schuessler, N5HYP
EM12ms
------------------------------
Message: 7
Date: Sat, 28 Nov 2020 13:01:38 -0600
From: <tjschuessler@???????.???>
To: "'AMSAT BB'" <amsat-bb@?????.???>
Subject: [amsat-bb] other used gear.
Message-ID: <02a901d6c5b8$e6d76b20$b4864160$@???????.???>
Content-Type: text/plain; charset="us-ascii"
On the same site https://www.mtcradio.com/ for their trade in used gear for
sale, as the Icom 910H they also show a Yaesu FT847 and also list an Yaesu
FT 818ND, but the picture connected to that list is for an Yaesu FT736.
Still might be work checking out for someone.
Tom Schuessler, N5HYP
EM12ms
------------------------------
Subject: Digest Footer
_______________________________________________
Sent via amsat-bb@?????.???.
AMSAT-NA makes this open forum available to all interested persons worldwide
without requiring membership. Opinions expressed
are solely those of the author, and do not reflect the official views of
AMSAT-NA.
Not an AMSAT member? Join now to support the amateur satellite program!
https://www.amsat.org/mailman/listinfo/amsat-bb
------------------------------
End of AMSAT-BB Digest, Vol 15, Issue 446
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