Category Archives: VHF

A small VHF/UHF driver

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I was searching for a small driver for 2m in order to have enough power for my microwave transverters. I usually drive them with about 500mW. Since i have a transverter block with about 0dBm output it needs some gain. Again i found something from China. The advertisement told something about 1.5W, the pictures showed a PCB with a print 35dB/3.2W. However, i thought it could be good enough to get 0.5W out of it.

A small VHF/UHF amplifier


When the device arrived i noticed that the manufacturer milled the top of the two amplifier IC. Very funny that the guys there try to save their designs from unwanted copy ;)
At the input there is a 6dB attenuation pad which are followed by two amplifier stages of unknown type. The first stage is supplied via a 5V regulator, the second one is connected to the supply input directly. I used 12V to do some measurements.
The first action was to know the gain of the circuit. I wanted to see if it is really working from 1 to 700MHz.
In the picture you see the little noisy measurement. The drive from the analyzer was set very low.

Gain of small VHF/UHF PA


From the gain curve it can be seen that the device is probably not working that well at the lowest end of the shortwave. But at least from 30MHz on it should be usable. Towards upper frequencies the gain is decreasing a lot but still 27dB at 700MHz. For the 2m band roughly 43dB gain is achieved and about 33dB in the 70cm band.
Finally i wanted to know which output power can be achieved in the amateur radio bands.

VHF/UHF PA output power


At about 1W output the output always gets compressed. You might add about 0.4dB on 70cm and 0.3dB on 2m to my measurements since the graph does not include the attenuation of the output cable. For me it means that the amplifier should work well for my purpose.

Searching for some FreeDV QSO partner on VHF

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Since i use Quisk for my HiQSDR i found it interesting to experiment with FreeDV again. Quisk can directly support using the FreeDV API and work in this digital mode without building lots of cables. Since i wanted to try the latest mode 700C i had to compile the library from the scratch and add the mode to the configuration of quisk. Below you can find recordings of my CQ call in the modes 1600 and 700C which were made loopback.
Now i search for a QSO partner preferably on 2m somewhere in the area around JO61. I can work relatively well direction southeast. So east OK might be good.

Mode 1600

Mode 700C

Please remember the 700C mode uses only 1kHz of bandwidth.
If you are interested in some tests just send me a email to dh5ym@darc.de

One season 4m …

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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

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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):

LZ1ZP 4m band SSB via ES on Aug/25/2017
Watch this video on YouTube.

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

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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.

My first QSO on 4m

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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.

IC-E92 spectrum

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Triggered by some forum discussion about interference risk of operating repeaters in neighbor channels in 6.125kHz channels I was curious about the TX spectrum of my IC-E92. The measurement was done radiated. I checked for neighbor channel interference. You can see the delta values bottom right.

FM wide:

IC-E92 FM wide 1750Hz

IC-E92 FM wide 1750Hz

FM narrow:

IC-E92 FM narrow 1750Hz

IC-E92 FM narrow 1750Hz

D-Star (only half span screenshot):

IC-E92 D-Star

IC-E92 D-Star

You can see that D-Star is really the most narrow band mode. Using neighbor frequencies at close QTH still cannot be suggested but at least the interference will be less than for narrow band FM.

March 16 V-/U-/SHF contest JO61VB

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This time i had to stay home. I used the little time to check the equipment for 2m.
In the end i had 37 QSO in about 3 hours of operation time. Not a lot. Given that i just use a omni antenna i am still fine.

March 16 - stations reached

March 16 – stations reached


I used my HiQSDR + ME2HT setup. This time i used a Odroid board with cwdaemon for keying. With that the rig can be placed anywhere in the house and the SDR/Log PC can be connected via wireless LAN. This enables contest operation from the couch without annoying the family by loud fans or clicking of RX/TX relais.

MMC2015@JO60TR

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Last weekend i was able to participate in the Marconi Memorial VHF Contest. First of all many thanks to DL4DTU and DL3DTS for giving the possibility to use their great QTH in JO60TR together with the antenna group 4x9ele + the amplifier !

I used my HiQSDR already few contests before. Now i wanted to try on 2m as well. I decided to purchase a ME2HT-Pro transverter which perfectly fits the transverter input/output of the transverter. You can see the setup on the picture below.

HiQSDR + ME2HT-Pro

HiQSDR + ME2HT-Pro

The SDR is controlled from the Quisk software. I usually use 196kHz bandwidth setting. This time i tried the CWSkimmer software. Quisk can forward the received baseband samples to a audio loopback device which is fed into the skimmer running under Wine.

The first time i used the very powerful Tucnak log from OK1ZIA. The log got the skimmer spots. In addition also Quisk connects to the skimmer. If the center frequency shifts Quisk tells the skimmer the new center frequency. This is required to always get correct spots. From the bandmap and the cluster window of Tucnak its directly possible to control Quisk like a hardware transceiver. In addition Quisk has a 2nd RX that can be used  to listen to other frequencies in between the CQ loops. The picture shows the SDR PC on the right side and log PC on the left side. On request of some OM i also fed the skimmer spots into the reversebeacon network. Sometimes i had the impression that this caused sometimes other stations beeing faster than me ;)

Log and SDR PC in JO60TR

Log and SDR PC in JO60TR

The big advantage of the skimmer connected to the local system was that i immediately noticed when DX stations were heading their antennas in my direction. Looking through the skimmer spots i noticed that i still missed quite some station from DX.

To avoid turning the antenna array all the time i decided to use a second antenna system. In addition to the 4x9ele of Norbert i mounted my DK7ZB-Oblong to one of the other masts at the QTH. The array ran with about 400wtts and the omni antenna with about 200wtts. Reception was selectable from either the one or the other antenna.

Overall the setup was working quite well. The only part that really caused a lot of trouble was the sequencer required to switch the various relais in the correct order. The microcontroller in the setup had problems to keep the PTT. Impulses from the switching relais caused the PTT input of the sequencer to raise for a short moment and afterwards the PTT was not detected anymore. Sporadically my transmissions got interrupted by that effect. Sorry for that. In addition i had some minor trouble configuring all the software correctly since the IP network setup was quite different than at home. I also had to extend my wireless internet access 2 times. One time because the Windows VM with the aggregator software wanted to download a Windows10 update ;)

In the next picture you see the map of the worked stations. The result was about 250QSO and a bit over 80000 points raw score with a average of about 300km per QSO.

QSO map mmc2015 from JO60TR

QSO map mmc2015 from JO60TR

Last but not least i want to show some spectrum screenshots from the contest.

The Erzgebirge is known to have a high density of VHF contest stations from OK and DL. Therefore the band is very full.

waterfall mmc15

waterfall mmc15

Within the waterfall history its a lot easier to find a free frequency than with a normal transceiver. You also see in which direction you need to move if one of the other close high power stations comes too close. For the close high power stations you can also see the problems of the different transmitters that can cause wideband interference.

Example 1: Phasenoise of the transmitter

poor TX phasenoise

poor TX phasenoise

This is really a poor example since the noise is less than 70dB below the carrier.

Example 2: Keying clicks causing splatters

keying clicks

keying clicks

In that example the spectrum of the oscillator is a lot better. But the hard keying of the TX causes leakage to other frequencies about 85dB below the carrier. The level was rather low but remember the proximity and the high antenna gain and TX power.

I wonder if someone can give me honest feedback about my own TX signal…?

73 de Mario, DH5YM