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G8MNY > TECH 03.09.22 10:33l 225 Lines 11116 Bytes #999 (0) @ WW
BID : 28726_GB7CIP
Read: GUEST
Subj: RTT Comms Test Set, Cal & Use
Path: IW8PGT<LU4ECL<GB7CIP
Sent: 220903/0924Z @:GB7CIP.#32.GBR.EURO #:28726 [Caterham Surrey GBR]
From: G8MNY@GB7CIP.#32.GBR.EURO
To : TECH@WW
By G8MNY (Update May 22)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
Now it is all fully working properly, extensively modified (see previous bul) &
calibrated (see below), the "Radio Telephony Test Systems" test set was made in
Feltham UK in 1987-9, & although old, it can do quite a lot...
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Þ /___________________________________________________________/Ý |
Þ³ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿³Ý |
Þ³³ÚÄÄÄÄÄÄÄ¿ÚÄÄÄÄÄÄÄ¿ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿ÚÄÄÄÄÄÄÄ¿ÚÄÄÄÄÄÄÄ¿³³Ý |
Þ³³³ \ AF ³³ \SINAD³³ù 5 3 9ú9 9 9 9 0 0 ³³ \MOD ³³ \POWER³³³Ý |
Þ³³³__\____³³__\____³³____________________³³__\____³³__\ ___³³³Ý |
ÚÁ³³o _ _ Oven _ _ Lock _ Rx ³³Á¿ |
³_³³ (_)_______(_) (ú) (_) o ù ! ! ! (_) ù ³³_³ |
AF³³o _ ³________³ _ _ _ _ .-. ³³ |
in³³@ (_) o o (_) (_) ! ! =(_) =(_) (_) o ( o ) ³³RF /
³³CTCSS Lis Vol MOD _ SIG GEN FREQ ú_ú _ _'-'_ ³³in/
³³123ú4 LS 1ú2 (ú) 1 2 3ú4 5 6 7 (ú) (ú) (ú)=(ú)³³ /
³ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ³/
~~Þ²Ý~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~Þ²Ý~~
TEST SET SPECIFICATION
RF Input N socket 50 Ohm 20dB Load atten. 1kW peak, 50W continuous
Power Meter 1-300W, 6 ranges (RF detection for Counter & Rx mode)
Frequency Counter 9 digit 1Hz-540MHz in 3 gate times & 10s averaging to 1Hz
Freq Reference Accuracy < 1/10^7/month, internal Xtal Oven & warming LED
Signal Generator PLL 100Hz steps from 10 - 539.9999MHz, O/P -13dBm (50mV)
Sig Gen Harmonics Better than -20dBc, Typically >-30dBc
Gen Attenuator 10x1dB & 8x10dB for 1.7uV-50mV, 40dB lower via Load Atten
Pilot tone(CTCSS) PLL 20-999.9Hz in 0.1Hz steps, Mod Level & Rx Counter readout
Modulation modes CW AM FM & PM
AF Osc 100Hz-15.9kHz or ext, Level adjustable
Ext Mod/AF out Needs >1V in, or gives 0-4V RMS AF out, 600 Ohm BNC
Xtal/IF 455kHz & 10.7MHz in built & ext Xtal socket & osc O/P BNC
AF Meter Bal/floating 3mV-10V, 8 10dB ranges, 11Hz-27kHz -3dB
SINAD meter Auto level, 1kHz Notch, 0 to -20dB/100-0% Noise & Distortion
Automatic Rx Scans 2MHz->1GHz, 100mW-300W Load input, up to 60dB S/N
RF & IF O/Ps Rear BNCs for RF & 450-470kHz IF
Rx AF Filters Comms -3dB 300Hz-3kHz, or HiFi -3dB 50Hz-15kHz
Modulation meter Auto Rx. +/- peak, AM 50/100%, FM 5/100kHz, PM 2/5 Rad
Monitor Amp & LS Vol & 1W for Listening to: AF in, SINAD, AF Osc, & Rx
Power AC IEC Mains input 230V/115 @ 60W, or XLR for 12V DC @ 5A
Weight 24kg in flight case
FULL CALIBRATION
The PSU has only a -20V preset, & test points for all other voltages. +26, 15,
8.5, 5, -12.
For AM FM PM calibration of the Rx module & for the for AF volts meter, I use a
"calibrated by design" source a "FeelTeck Dual DDS Oscillator FY6600-60M".
(This is despite it having an AM depth meaning "% number" issue, & P-P values
needed.) Underside of Rx box are presets for FM PM & AM calibrations. The AF
voltmeter PCB has a cal pot too.
Auto tune Rx box has internal presets inside the inner RF box (as shown in
earlier bul). Set STOP preset for reliable action, then tune IF coils for
narrow bandwidth (scope IF O/P with wide dev sweep) & constant level from AGC
for AM, centred AFC action with FM discriminator for FM & PM mode just giving
identical +/- 100kHz readings.
Rx Splitter atten preset (small hole to bias DC into diodes in Tx mode)
adjustment needs to be enough so, no Rx overload occurs on an AM signal @ 300W
carrier (3W after load), & still leaves good Rx sensitivity @ 500mW (5mW after
load).
Once the Rx is calibrated, it is easy to check the sig gen is working correctly
against it & the counter is functioning correctly. Inside the RF oscillator box
there are presets for the RF AGC, 6 AM bias pots for each osc & they are
adjusted for best modulation shape over each osc range, checked with a scope
from Rx IF for the 4 lower PLL tuned circuit freq centering. FM deviation
modulation sensitivity varies depending on the varicap voltage needed for the
frequency, so +/- 100kHz deviation is not possible at all frequencies.
SINAD meter cal with its AGC, is done with the AF osc patched from the AF Osc/
Rx mod O/P, & for the 100% level set frequency to 2-3 kHz, then @ 1kHz the 2
null pots adjusted, for lowest 0% reading (listen Sinad O/P). The AGC range can
cause some slight distortion, so calibrate over the AF level range needed.
CTCSS Frequencies are accurately clocked from the 4 dig thumbwheel data, so
should be accurately seen on the counter with the CTCSS measure button. For
lowest distortion, set @ 300Hz & scope (distortion analyse) the Rx wave shape &
adjust the + & - clippers for best shape. Adjust the set square @ 800Hz, LF
correction 8/ pot @ 50Hz & redo for best results again. Distortion was < 2% 50-
800Hz.
AF Osc, the 160 dial up frequencies were trimmed with added Wayne bridge caps
for the LF end, & gain setting caps around the op amp for the 15.9kHz. All are
now within 1% as measured on counter. Distortion is < 0.3% (-50dB) @ 1kHz.
RF Frequencies are clocked from the 7 dig thumbwheel data & PLL so should be
accurate if reference is OK. For calibrating the reference oven, I use a scope
& view a 1MHz locked from a 198kHz off air standard, with the sig gen's 10MHz &
adjust for no drift when it is properly warmed up (10mins). This calibrates the
9 digit counter too.
RF Level should be -13dBm measured with atten set to max level at the pre-Load
Atten BNC link. Adjustment is the ALC present inside the nested Osc box. Level
flatness (+/-0.5dB 10MHz-539.9MHz). Each Osc coil is tuned for good PLL lock
voltages on band edges. RF harmonics & sig gen's 90dB atten checked @ all
frequencies on spectrum analyser. And the 300W dummy 20dB atten load & Splitter
box 20dB with analyser tracking gen.
Power meter has 6 presets for the 6 power ranges. These have only been compared
with other meters occasionally & itself on range steps.
IN USE
Tx MEASUREMENTS
===============
1/ Tx connected to N socket of the 300W Load atten input you can measure...
ÚÄÄÄ¿ ÚÄÄ¿ ÚÄÄÄÄÄÄÄÄÄ¿ a) Tx power 0.1-300W with 6x 10dB power ranges.
³PSUÃÄ´TxÃ>Ä´ Test set³
ÀÄÄÄÙ ÀÂÄÙ ÀÄÄÄÄÄÄÄÄÄÙ b) Frequency 1Hz - 540MHz to 1Hz res (1 or 10s gate).
Mic
c) FM Dev 0-5kHz, 0-100kHz, PM 0-2Rad, 0-5Rad, &
AM Mod 0-50%, 0-100%.
d) CTCSS frequency, & Dev @-20dB (e.g. max +/-250Hz?)
e) Hear the FM/PM/AM modulation on Test set's LS.
2/ Tx connected to N socket of the 300W Load atten input you can measure...
ÚÄÄÄ¿ ÚÄÄ¿ ÚÄÄÄÄÄÄÄÄÄ¿ a) With external spectrum analyser after
³PSUÃÄ´TxÃ>Ä´ Test set³ the 20dB high power atten & 20dB splitter
ÀÄÄÄÙ ÀÂÄÙ ÀÄÂÄÄÄÄÄÄÄÙ (40dB less), but the power meter's diode
Mic BNC³ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿ load increases some of the harmonics!
LinkÀ´Spectrum Analyser³
@-40dB ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ b) Other Tx spuri can also be safely seen.
or a Scope on HF
3/ Tx connected to N socket of the 300W Load atten input you can measure...
ÚÄÄÄ¿ ÚÄÄ¿ ÚÄÄÄÄÄÄÄÄÄ¿ a) With a scope connected to IF output
³PSUÃÄ´TxÃ>Ä´ Test setÃ>Ä¿Rx & 2nd Beam or Trigger from Rx AM Mod
ÀÄÄÄÙ ÀÂÄÙ ÀÄÂÄÄÄÄÄÄÄÙ ³AM then AM modulation lineararity, or
Mic IF³ ÚÄÄÄÄÄÄ¿ ³mod any AM Hum can be seen.
outÀ>´Scope ÃÄÙ
ÀÄÄÄÄÄÄÙ
4/ With Rx AF mod BNC patched to AF input banana sockets on test set.
ÚÄÄÄ¿ ÚÄÄ¿ ÚÄÄÄÄÄÄÄÄÄ¿ a) FM/PM/AM Tx Signal Noise to <70dB can be measured
³PSUÃÄ´TxÃ>Ä´ Test set³ via the Comms or Hifi filters.
ÀÄÄÄÙ ÀÂÄÙ ÀÄÄÄÂÄÄÄÄÂÙ
Mic ÀÄ>ÄÄÙ b) Hear the FM/PM/AM Tx noise on Test set's LS.
Rx AF
5/ Mod AF Osc BNC out patched to Mic (or acousticly) with a suitable atten/pot.
ÚÄÄÄ¿ ÚÄÄ¿ ÚÄÄÄÄÄÄÄÄÄ¿ a) FM/PM/AM Tx Distortion can be measured on SINAD
³PSUÃÄ´TxÃ>Ä´ Test set³ Meter & hear notched distortion on Test set's LS.
ÀÄÄÄÙ ÀÂÄÙ ÀÂÄÄÂÄÄÄÄÂÙ
MicÀÄÄ<ÄÄÙ ÀÄ>ÄÄÙ b) FM/PM/AM modulation freq response 100Hz-15.9kHz.
AFMod Rx AF Read on AF meter's dB scale. (e.g. -40dB @ 4kHz??)
1kHz SSB response only done to the power meter.
c) Single Sideband actual Tx freq measured.
Rx MEASUREMENTS
===============
6/ Rx patched to load N, or BNC after stepped atten. for 40dB more (50mW max).
ÚÄÄÄ¿ ÚÄÄ¿ ÚÄÄÄÄÄÄÄÄÄ¿ a) FM/PM/AM Rx can tested for freq error & selectivity
³PSUÃÄ´RxÃ<Ä´ Test set³ with siggen set to correct or off +/- frequency.
ÀÄÄÄÙ ÀÄÄÙ ÀÄÄÄÄÄÄÄÄÄÙ
Mod on/off b) Rx CTCSS recognition, dev & sensitivity checks,
with & without comms mod present.
c) Rx S meter calibration checks. (S9+20dB HAHA!)
d) Rx Image Rejection, put in +/- 2x IF frequency etc.
& check RF level needed compared to normal Rx.
7/ Rx patched to load N, & Rx LS to AF input banana sockets on test set.
ÚÄÄÄ¿ ÚÄÄ¿ ÚÄÄÄÄÄÄÄÄÄ¿ a) FM/PM/AM Rx Frequency response seen on dB scale.
³PSUÃÄ´RxÃ<Ä´ Test set³
ÀÄÄÄÙ ÀÂÄÙ ÀÂÄÄÄÄÄÄÄÄÙ b) FM/PM/AM Rx Distortion @ 1kHz on SINAD meter.
LSÀÄÄ>ÄÄÙAF 1kH or
.1-15.9kHz c) FM/PM/AM sensitivity MEASURED in uV/dBm, siggen set
& 1kHz modulation for 12dB SINAD.
d) FM/PM/AM max S/Noise (hum etc).
Sinad meter is used for best Rx S/N sensitivity & FM discriminator adjustments.
For that, 5 turns of the LS lead on a ferrite ring, stops it being an added
aerial on weak test signals! RF & DC leads may need the same treatment!
CONCLUSION
==========
All of the above 21 rig tests, also permit rig adjustments to improve things.
With SSB kit AM mode has to be used to the Rx only. But SSB Tx 2 tone tests can
be done using CTCSS & beating AF osc (e.g. 0.8 & 1kHz) from mon LS to the mic &
scoping the Tx RF envolope (200Hz) beat note on a seperate dummy load.
So a useful lab or /P test set. A one stop shop for all rigs, when taken to my
local club's regular test & fixit evenings.
See my tech Buls on "RTT Comms Test Set", Analyser Takeda Riken TR4122B", "AF
Waveform Generator (RS)", "RTT Mod Meter (100)", "FeelTeck Dual DDS Osc FY6600
-60M", "Marconi Distortion Meter TF2337","Marconi 2019A Sig Gen"," Systron
Donner 1702 Sig Gen" "Marconi Counter Type 2432A", "198kHz Off Air Standard",
"Comparing Off Air Freq Standards", "Off Air Lock for Ref Osc", & "Scope RF
Trick".
Why don't U send an interesting bul?
73 de John, G8MNY @ GB7CIP
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