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Reviews For: UR3LMZ Dual band Ukraine / Ebay transverter

Category: Transverters

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Review Summary For : UR3LMZ Dual band Ukraine / Ebay transverter
Reviews: 1MSRP: 150$
Description:
A simple and cheap 144Mhz/432Mhz to 28Mhz low power transverter
Product is in production
More Info:
# last 180 days Avg. Rating last 180 days Total reviews Avg. overall rating
0012
ON6AB Rating: 2021-03-22
A DIY project Time Owned: 0 to 3 months.
1- The transverter
This is a cheap 150$ 144Mhz / 432Mhz transverter which is available from Ebay. Is was designed by UR3LMZ which seems to be also the original designer of the “Transverter-store “ Ebay transverters. Needless to say, This transverter comes from Ukraine.
The design is simple and clever. They use what they call a Highly stable frequency synthesizer which can be switched to 2m and 70cm frequencies to mix with the incoming signal in a nice Mini-Circuits ADE-1 mixer. It is possible to cover the complete USA 2m band in 2Mhz segments by using the F+ switch which sets the synthesizer 2Mhz higher.
Separate TX drivers for 2m and 70cm are used and combined again into a single RD01 / RD15HVF1 final stage.
On the RX side, a BF998 pre-amplifier stage is used for each band and the signal is fed into the same ADE-1 mixer.

2- Delivery
a. The transverter took six weeks to arrive after ordering on Ebay.
b. It was delivered in a seemingly used carton box and the packing was only ok. There was only just enough protective material to avoid damage during transport.

3- Build
a. All connectors and switches seem to be of good quality.
b. The PCB looks very professional and components are nicely soldered.
c. A barely readable schematic diagram is delivered with the unit. However, there is no pcb lay-out and there is no component identification on the pcb neither.
d. The back plate is used as a cooling plate for both the IF attenuator 50W resistor and the VHF/UHF final transistor, unfortunately front and back plates are made of stainless steel (more about this later).
e. The frequency sensitive circuitry (TCXO and PLL) is mounted near the front plate on a separate pcb.
f. There were no rubber feet delivered with the housing. It is highly recommended to add some in order not to damage the area were the transverter is put on.

4- PTT and VOX
a. The transverter is equipped with a VOX circuit to switch between RX and TX. There are no settings to alter the sensitivity of the vox, nor is there a potmeter to set the vox delay.
b. The transverter is NOT equipped with a PTT connection but that can be added afterwards keeping the vox operative as some kind of extra insurance to avoid damage by transmitting into the receive end.
c. I added a Cinch PTT connector which activates the relay K3 by pulling it to ground. In normal VOX operation, the relay is pulled to ground via the AZ431 shunt regulator driven by an RF detector circuit consisting of VD6, VD3, C5 and R3.
d. In my opinion, the addition of the PTT circuit is a must. All transverters should be delivered with PTT and not solely rely on a VOX circuitry.

5- Receive performance
a. The transverter set-up with the FLEX3000 as IF receiver is compared to the FT817nd transceiver which has a reasonably sensitive VHF receiver.
b. Comparing the PI7BRG beacon strength and FT8 signals, the sensitivity of the transverter – FLEX3000 combination definitely has the edge over the FT817nd.
c. The IF receive 28Mhz output moves the FLEX3000 S-meter to a constant S9 level.
I reduced the signal to the 28Mhz receive amplifier by adding a 470pf capacitor to ground at the input of Q1 BFR193. Depending on your HF receiver, this value may vary between 100 and 470pf. It might also be that it is not needed at all.

6- Transmit performance
The 144Mhz design of the transmitter section seems not to be optimized for a drive of 5W to 10W IF.
With an 28Mhz input of only 0,5W the 144Mhz output is 9W.
With 1W at the input, the transmitter is already overdriven.
That is with the RV1 attenuator setting for maximum attenuation.
The maximum attenuation of the attenuator section is 34dB which seems to be normal. (40dB is given in the technical specifications).
With 5W input, the output to the mixer is 2mW which is typical. The maximum input power of this ADE-1 (Mini circuits) mixer is 50mW.
The problem is probably too much gain in the 144Mhz driver circuit.
I fixed this by replacing R25 (100 Ohm) by a 1k2 value.
Doing so, the 144Mhz output power can be nicely set with RV1 with common input powers of 0,5 to 10W.
I’m not sure this is the correct way of doing things but it seems to work.

The 432Mhz transmitter section does not have this problem.

7- Stability
The stability is acceptable for doing digital modes.
As I’m currently using the transverter only on 2m, I only did a test for that band:
There is a drift up to 5 Hz on 144Mhz during an FT8 QSO with sometimes sudden shifts as large as 10Hz. They probably are caused by ambient temperature variations near the master oscillator board. If I blow on the board, I can cause the same shift.
I tried to minimize shift by incapsulating the synthesizer board in Styrofoam. Is seems to add stability.
Tests now show a drift of 10Hz from cold power-on to + 3 minutes.
8Hz from 3 minutes to 10 minutes
3Hz from 10 mintues to 20 minutes
2Hz from 20 minutes to 30 minutes.
An additional 1Hz after 30s transmit with 5W (2m).
No additional drift after an additional 30s transmit with 10W
An additional 3Hz after a 60s transmit with 10W.
After that, the transverter very slowly shifted another 3Hz because of the slowly increasing temperature of the housing. Rather stable I would say.

8- Cooling
The power FET, attenuator resistor and voltage regulator are all screwed to the back- or front plates.
Any cooling is virtually inexistent.
Indeed, by using stainless steel as front and back plates, the thermal conductivity is extremely bad.
Thermal conductivity of aluminum is 205 W/m K. Copper is an even better heat sink material and has a value of 385. Steel only has a value of 50 and stainless steel is only 16 W/m K which is one of the worst metals to use as a heat sink!
The power FET is screwed to the backplate with thermal paste. Not really very helpful.
Don’t touch the FET, nor its M3 screw to the back plate! You’ll burn yourself!
The back plate itself does not get warm ( what a surprise ;-).
If you use this transverter as it is delivered from factory, the RD15HVF1 power FET will be roasted in no time!
I replaced the stainless back plate by a homemade aluminum one and added a heatsink to the back. The RD15HVF1 now only gets barely hand-warm.
I also added an internal heatsink to the voltage regulator IC which is screwed to the front plate. (I left the front plate unchanged => stainless steel).

9- Conclusion
Although it is sold as a ready-build unit, this transverter has to be considered as a DIY project. The idea behind it is clever. The realization is not.
This is what you need to do before using it:
- You need to replace the back plate with a custom made aluminum one.
- You need to mount an additional heat sink to the back plate.
- You need to mount a heat sink inside the housing for the voltage regulator.
- You need to alter the drive level to the final stage by replacing a resistor.
- You need to add a PTT connector.
- You need to add rubber feet to the housing.

After the mods, you end up with a frequency-stable and cool running transverter with a better sensitivity compared to the FT817nd. Not bad at all.
If you use it at 5W, the RD15HVF1 is known to put out a clean signal, ready to drive your amplifier. Here also, the transverter IMD performance at 5W output is better than the FT817nd at 5W output.