29 October 2013

Transverter 29/70, RX current consumption

I found no mention online about current draw of the Ukrainian 29/70 transverter: my specimen drains about 24 mA at 12V in reception.

More to follow, especially a TX test once I found what is a suitable heatsink: just the containing box (yet undefined) or something larger?!

If everything works, the construction of a simple sequencer will follow. Most probably based on one of my (I)FR(K) projects.

27 October 2013

Transverter 29/70 arrived and switched on

The "ten to four metres" transverter has arrived from Ukraine. The very first impression is that it is indeed SMALL! A picture-to-real comparison with the original 10-to-2 m transverter shows that coils are different, so it has somehow been retuned to 70 MHz. Look at it on a 5€ note:

First on-air test was the reception of the local beacon. I started closing the output on a 50 ohm load "just in case" (yes, I know the load shown is not able to handle more than 0.5W). Then about 4 m of RG58 going to the FT817 tuned on 29 MHz: the local beacon was coming through S7, with the dummy load as antenna! Actually, dummy load or not, it made no difference.

The transverter circuit is very very very simple (and I have spotted one error on the included diagram), but the RX chain is hot. Using the same coax length on the IC706 tuned to the beacon frequency resulted in the same signal strength. So, apart from RF leakage, it is a (good?) sign of life.

14 October 2013

Packed up RTLSDR

A local HAM agreed to compare his 23 cm transverter with the RTLSDR in order to see if the little stick can be competitive in certain situations, like a contest. So I needed to do some adjustments to my typical home setup.

First of all, his cables terminate with N connectors. I initially though of changing the short RG174 cable end into a female N, but quickly realised how weak the whole system would be considering the weight of N and in-flexibilty of thick coax. I needed to protect the dongle with a box.

I picked a metallic chocolate box I kept aside some months ago and fitted a flanged N female. While I was at it I also shortened the RG174 cable to what was strictly necessary (1 metre to 10 cm): these two actions resulted in at least a couple of dB gain (or ... "less loss"). Note that 1m of RG174 at 1300 MHz looses 1 dB.

The USB hole is not something I am proud of, but it was realised in less than 5 minutes, so it is acceptable for this experiment. If the on-the-field comparison shows RTLSDR is a decent performer I will consider soldering directly into the PCB both the USB cable and the N or BNC female head.

01 October 2013

Transverter 29/70

While searching online for parts for a 70>23 cm tripler I came across an auction for a 10m to 4m transverter board. Just the fully assembled board and an A4 sheet with instructions.

It is supposed to output 5W on 70 Megs with 150mW drive on 29 MHz. It should be all-mode. It needs a heatsink, housing, wiring, IF attenuator and RX/TX sequencer.

Looks like a good companion for the FT817. Time will tell, since I bough one of those.

Edit: (At the time writing there is one board left in Ukraine)