A chinese PA for 6cm

Some posts ago i wrote about my new 6cm transverter. I already did a few QSO and i got a 10W PA for a good price. Unfortunately this PA needs 1W of Input and the transverter gives maximum of 250mW output. So a small “driver” is needed. I was researching the options but found no easy solution that also fits my budget constraints. Then i saw some amplifiers sold as WLAN amp. Usually those are for 2.4GHz but i thought if there are some for the one band there are probably also some for the 5GHz band. During the search i found the nice Amp on the picture below that is sold as an amplifier for video transmissions for about 22Euro. It is specified with 3.5/4.5W. But whatever output power for the price i thought i cannot do wrong a lot.

A chinese 5.8GHz PA

When the device arrived i had to find out the supply voltage. In fact it works with 12V and a first test confirmed it has some gain. The bad thing was that the connectors were reverse SMA and for each connector it was quite some gap between the connector and the PCB. So i thought, “thats a strange matching method” ;)
After removing the soldered shield on top of the PCB one of the screws for mounting the heatsink also came out.
The semiconductors used in the PA are 2x Skyworks SE5004L with a P1dB of 30dBm typical and 34dBm max. So i thought 2W should be possible at least. The gain is specified with 32dB. At the input of the PA is a pi-attenuator.
Later i soldered some nice SMA jacks and then the PA went to storage for quite some while.

The “inner values” of the small amplifier

Now i found some minutes to remove the attenuator and do some raw measurement of the output power. The gain of the amplifier is about 28..29dB. I did not measure the cable attenuation exactly so do not nail me down on the last dB.
The input vs output figure you can find below. The P1dB is about 2.5W. So considering the samples to be typical there is quite some loss on the PCB. But even in that case for the given price its a nice thing.

5.8GHz video PA output power

One season 4m …

Yesterday the 4m TX permission in DL ended for this year. Hopefully we get another one next year. For me it was the first time and it was rather interesting to compare real band opening with the propagation prediction on dxmaps. Unfortunately i missed the big ES in June. I was on vacation and also my transverter was not ready that time. But still i made some QSO.
A frequent “beacon” on the band was DK2EA. We had several short qso and it was always a stable connection although we both used low power and small antennas.
During the ES openings i worked EA, EI, SV and LZ. I also worked some OK stations and some local stations as well.

While i was using my FT-817 as IF TRX last days i hooked up my HiQSDR to the transverter.
The day before yesterday i noticed some band opening to G. I heard the beacons GB3ANG and GM8RBR. You can see the screenshot below. While GB3ANG was rather stable over a long time GM8RBR more in the north was fading in and out all the time.

4m ES 2017-08-30


I also heard GM4ZMK calling CQ. Unfortunately outside the frequency range allowed for TX in Germany. The opening to him was only few minutes.

Find the audio files here:

GB3ANG/B 20170830

GM8RBR/B 20170830

GM4ZMK 20170830 calling CQ

DG3LSM 20170830 local

Now i will disassemble my 4m station and switch to other activities. Hope to hear you on this nice band next year.

Another 4m ES

Last week i met another ES opening and worked LZ1ZP and LZ1ZX. I also heard the LZ2HV beacon and once again SV2JAO/B.
LZ1ZP was extremely strong. Here you can find a short video of his signal in SSB (29MHz = 70MHz with transverter):

Below you find some audio snippets of ES signals i recorded the last weeks.

2017-08-03 4O0BCG/B

2017-08-03 SV2JAO/B

2017-08-25 LZ2HV/B

2017-08-25 LZ2HV/B

2017-08-25 LZ1ZP CW

2017-08-25 LZ1ZP SSB

Another lunch time ES

Today i was lucky again. During lunch i worked LZ1AG and OK1VBN. Heard the beacons SV2JAO/B and 4O0BCG/B. Also 9A/S51DI/P came back to my CQ, but i did not manage to copy the complete call. Sorry! Unfortunately i did not have a 2m rig available since the band was also open on 144MHz.

Almost a antenna feed for 6cm …

Not all things work out… I was searching for some nice feed for a offset dish to be used for 6cm narrow band. In the internet i found a nice version from Russia.
It was announced for the 5GHz WLAN band without dedicated specification of the exact frequency.
For 40 Euro including shipment it was ordered and after only 2 weeks in transit (russian saying tells: For bad children Santa Claus sends the gifts by russian post… ;) ) and 1 week in customs i finally got my russian present.

5GHz horn from Russia


Measuring the input matching shows that its well in the middle of the lowest 5GHz WLAN band.

WLAN horn matching measurement


Far away from 5760MHz. But ok, lets try. First i removed the N connector.

5GHz horn from Russia


The connector with the radiator seems to be a robust construction. I tried to shorten it step by step. Unfortunately it happened what could be expected. The feed can be de-tuned to about 5.5GHz but above that the matching vanishes. Probably the distance to the backside of the horn is too big. So this one was a fail. Fortunately i can still use it for WLAN if i make the radiator a bit longer again. If you want to use the lowest of the 5GHz bands it is really a nice and very solid construction.

MD380 DMR radio

I have a Tytera MD380 DMR transceiver now. Flashed latest MD380tools and database yesterday and hope to make a first qso soon. A mmdvm hotspot is in the pipeline but i still need to connect a transceiver.

TYT MD380 DMR radio

Wideband amplifier

I tested my new assembled wideband high IP amplifier (BX-088) from Funkamateur. The transformers need to be handmade which is a very fiddling task. The cores are really small. I choose for 11dB gain assembly. The measurement shows, that the gain really rapidly drops below the 160m band. The figure fits to what is shown in the documentation. So far i did not measure the p1dB or IM3 behavior.
The points that are interesting for me are 28MHz as LNA for my SDR or as IF amplifier for transverter input on 14/28MHz and usage as pre-amp for 70MHz.

Measurement of Funkamateur wideband amplifier

My first QSO on 4m

Now finally i have my 4m rig ready. It consists of a DF2FQ transverter with some modification to power module mounting and RX amplifier stage.
Currently i use my FT-817 to drive it. I also added a separate drive input which i need for the SDR. With 1mW input on 29MHz it can achieve about 25W output on 70MHz.
So far i did not benefit from ES conditions. Seems it missed all the nice propagation from last weeks. Hopefully there will be another opening until end of August, when the permission ends here.
As antenna i use a Hentenna Quad with direct 50Ohm assymetric feed point. The antenna has some significant Null in the radiation pattern but is a good compomise for the fibre mast at the balcony.
My fist contact was with DK2EA in JO50UF in CW. Meanwhile i also worked DD1VD and DL2VPO locally.

4m band rig on the balcony

4m Hentenna Quad

[Edit 2017/07/23] meanwhile i worked EA1BFZ in IN81SS and today SV2JAO in KN10DN. ES propagation seems to be very short and spotty. You really need to look to the cluster and search the frequencies all the time. 5 minutes later all could be gone. 100km away the conditions can be significantly different.