SARTS Repeaters

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Daniel Wee
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Re: SARTS Repeaters

Post by Daniel Wee »

Preliminary findings:-

1. The output VCO is producing a -1.3dBm repeated signal on 200.175MHz to 200.224MHz. The PLL is not locking and the TUNLK signal is not going high. For some reason, the PLL does not appear to be working.

2. Post TXVCO amplifier chain voltages appear to be correct.

3. 15.3MHz output from X1 into TX PLL IC3 (LMX2352TM) for OSCIN is correct.

4. The OUT1 from the TX PLL IC3 which becomes TXVCO_SW is not working.

5. The FO/LD from the TX PLL IC3 which becomes TUNLK is not working.

6. The CPORF output from the TX PLL IC3 which feeds TXVCO1/2 is therefore not locked.

The part in question is the LMX2352TM which appears to be no longer manufactured.

Testing the RA60H1317M RF Module

7. The module was fed directly with 145.625MHz at around -5.72dBm to the input pin (50ohms matched) and the output was measured at 30.52dBm. So we're seeing a gain of about +36.24dB on the power here. According to the chart below, the expected power gain is around +38dBm so we're in the ballpark. The module is likely to be working.

RA60H1317M performance.png
RA60H1317M performance.png (110.13 KiB) Viewed 480 times
Attachments
LMX2352TM-National-Semiconductor.pdf
(411.6 KiB) Downloaded 22 times
Daniel Wee
Site Admin
Posts: 2422
Joined: Wed 25 Feb 25 2009 8:00 pm

Re: SARTS Repeaters

Post by Daniel Wee »

Potential source for the PLL chip (LMX2352TM):-
https://www.radioparts.com/catalogsearc ... =LMX2352TM

UPDATE: They only have the LMX2306TM and not the LM2352TM
Daniel Wee
Site Admin
Posts: 2422
Joined: Wed 25 Feb 25 2009 8:00 pm

Re: SARTS Repeaters

Post by Daniel Wee »

Telewave TPRD-1544 retuning results

TX insertion loss
TX insertion loss
TX~ANT2.png (15.64 KiB) Viewed 450 times
RX insertion loss
RX insertion loss
RX~ANT2.png (15.47 KiB) Viewed 450 times
TX-RX isolation
TX-RX isolation
TX~RX2.png (15.09 KiB) Viewed 450 times
SWR looking into TX port with dummy load ANT
SWR looking into TX port with dummy load ANT
TXSWR2.png (16.41 KiB) Viewed 450 times

Final results
TX insertion loss = 2.20dB
RX insertion loss = 2.71dB
TX-RX isolation @145.625MHz = 87.49dBm
TX-RX isolation @145.025MHz = 78.51dBm
TX SWR = 1.18
Daniel Wee
Site Admin
Posts: 2422
Joined: Wed 25 Feb 25 2009 8:00 pm

Re: SARTS Repeaters

Post by Daniel Wee »

Retuned the Sinclair Q2330E cavity:-
TX~ANT.png
TX~ANT.png (15.33 KiB) Viewed 467 times
RX~ANT.png
RX~ANT.png (15.51 KiB) Viewed 467 times
TX~RX.png
TX~RX.png (15.75 KiB) Viewed 467 times
TXSWR.png
TXSWR.png (16.71 KiB) Viewed 467 times

Final results:
TX insertion loss = 1.46dB
RX insertion loss = 1.68dB
TX-RX isolation @145.625MHz = 97.43dB
TX-RX isolation @145.025MHz = 91.24dB
TX SWR = 1.06
Daniel Wee
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Posts: 2422
Joined: Wed 25 Feb 25 2009 8:00 pm

Re: SARTS Repeaters

Post by Daniel Wee »

Improved tuning procedure using only insertion loss measurement:-

1. With a T-connector, tune individual cavities. This can be done with the complete harness in place but only one of the two or three cavities connected at one time for tuning. Doing so saves an extra step (#5).

2. Set the scope center frequency to the pass frequency and set a marker on it. On the pass frequency, adjust rod until insertion loss is minimal. To do this with great accuracy, zoom in with a 200kHz SPAN and high gain. Use the readout value rather than visually looking for a peak as that is unreliable. (This step of setting the pass point can be done using an SWR reflection bridge and setting for the lowest SWR possible. It appears that the SWR method makes it easier to pinpoint the peak. In theory the two should yield very similar answers.)

3. Set the scope center frequency to the reject frequency and set a marker on it. On the reject frequency, adjust the capacitor until you get the maximum rejection and deepest notch. To do this, use SPAN of 200kHz and high gain, using REF OFFSET to zoom into the notch.

4. Connect a 50-ohm dummy load to the terminating port of the side that is not being tuned. Connect the TG output to the terminating port of the side that is being tuned. Connect the RF input to the antenna port of the harness.

5. Connect the cavities individually, one at a time. Use the rod to move the notch to the reject frequency. Once again, this needs to be done with high resolution so use the settings in step #3. Do this for all the cavities, one at a time.

6. Connect all the cavities to the harness. If everything is done correctly, at this point, everything should just align without needing further adjustment.
Daniel Wee
Site Admin
Posts: 2422
Joined: Wed 25 Feb 25 2009 8:00 pm

Re: SARTS Repeaters

Post by Daniel Wee »

Retuning the Sinclair Q2330E using the aforementioned method yielded better looking curves and better symmetry. The SWR curve, however, still looks messy.

TX-ANT insertion loss
TX-ANT insertion loss
TX~ANT.png (15.41 KiB) Viewed 449 times
RX-ANT insertion loss
RX-ANT insertion loss
RX~ANT.png (15.41 KiB) Viewed 449 times
TX-RX isolation
TX-RX isolation
TX~RX.png (15.59 KiB) Viewed 449 times
SWR looking into TX port with dummy load ANT
SWR looking into TX port with dummy load ANT
TXSWR.png (16.77 KiB) Viewed 448 times

Final results:
TX insertion loss = 1.47dB (35W input required for 25W output)
RX insertion loss = 1.78dB
TX-RX isolation @145.625MHz = 97.38dB
TX-RX isolation @145.025MHz = 97.05dB
TX SWR = 1.08
Daniel Wee
Site Admin
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Re: SARTS Repeaters

Post by Daniel Wee »

Candidates for replacement repeater:-

Daniel Wee
Site Admin
Posts: 2422
Joined: Wed 25 Feb 25 2009 8:00 pm

Re: SARTS Repeaters

Post by Daniel Wee »

We now have the Motorola SLR-5300 installed and working. Cavities are tuned. Currently using the Yagi antenna on the upper balcony with SWR of about 1:1.4 measured at the TX port of the cavity. The radio does not overheat, nor drift appreciably in frequency with heavy usage. As the repeater now comes with its own PSU, the external PSU is no longer needed. The cables between the repeater and the cavity have also been changed and now use Belden 7806A cables.
Attachments
20210909_132157[1].jpg
20210909_132157[1].jpg (2.3 MiB) Viewed 284 times
20210909_132248[1].jpg
20210909_132248[1].jpg (2.36 MiB) Viewed 284 times
20210909_132150[1].jpg
20210909_132150[1].jpg (1.83 MiB) Viewed 284 times
Daniel Wee
Site Admin
Posts: 2422
Joined: Wed 25 Feb 25 2009 8:00 pm

Re: SARTS Repeaters

Post by Daniel Wee »

The current setting for the repeater:-

TX 145.625MHz
RX 145.025MHz
CTCSS 156.7Hz
Output power 25W
Time-out-timer 1-minute
Mode: Analog

The plan is to get the license for the CPS software so that we can adjust these values. This requires a license key and is tied to the laptop on which the software is installed.

Furthermore, we seem to be experiencing occasional QRM that occurs mostly at night. The QRM does not appear to key up the repeater (due to the CTCSS) but can be heard when the repeater is keyed up. It overpowers weaker signals. The plan is to:-

1. Install a monitoring receiver at the repeater site
2. Place a spectrum analyzer at the site for the same purpose

Additional work to be done:-

1. Install a Diamond X200 VHF/UHF vertical and do A-B comparisons with the yagi.
2. Re-program the repeater for a longer ToT duration (5m or 7m)
3. Possibly increase output power to 35W to account for the 1.5dB insertion loss through the cavity
4. Possibly put repeater into dual-mode

To do this, currently:-

1. Purchase license from Motorola
2. Source mounting post for antenna
3. Purchase UHF-N-male adapter for the PL-259 terminated cable
4. Prepare Remote SDR on RPi4 with HackRF for deployment at site

Separately - LMX2352TM/NOPB is on order from Icom for the possible repair of the ICFR-5000. This is due sometime in October.
Daniel Wee
Site Admin
Posts: 2422
Joined: Wed 25 Feb 25 2009 8:00 pm

Re: SARTS Repeaters

Post by Daniel Wee »

The Motorola CPS 2.0 software is used to program the repeater profile but an RNDIS driver is required before Windows 10 recognizes the USB port as a network device.
Attachments
MN006055A01-AE_enus_MOTOTRBO_Customer_Programming_Software_CPS_2_0_Online_Help.pdf
(5.68 MiB) Downloaded 10 times
motorola-slr5500-en.pdf
(3.43 MiB) Downloaded 12 times
MOTOTRBO_drivers.zip
(6.93 MiB) Downloaded 14 times
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