Now i started soldering the 9cm transverter kit that was in the shelf since years. The filter caps look already a bit oxidated. But soldering still worked fine. The new 9cm will get into a box together with 13cm at some time.
I assembled the Iceni 70cm transverter kit from G4DDK. Instead of the ADE-13 i used a ADE-751MH+. Sam was so kind and sponsored one of his mixer samples he used for testing. Unfortunately the manufacturer of the mixers uses different pinouts for almost every type. In this case i had to swap RF and IP ports. The good one: It is not difficult with the layout. In the picture you can see the short semirigid.
G4DDK Iceni transverter for 70cm
The next picture shows some IM3 measurement for the RX part of the transverter. The estimated input IM3 point is around 0dBm now (21dB gain).
The P1dB is about -9dBm (2x -12dBm).
Iceni ADE-751 IM3
I also checked the output signal. The 2nd harmonic is about 53dB below wanted signal and the LO suppression is about 58dB. So some extra filter might be required to the comply with regulations.
Overall i am very satisfied with this transverter block. With the alternative mixer the performance is even better than it was before.
Next i need to add a amplifier and other unimportant things like sequencer, RX/TX-switch, chassis and so on ;)
For my 6cm transverter i bought a 10W DL2AM PA years ago. Because it needs about 1W drive i combine it with the WLAN PA from here
The complete chain now has about 39dB gain and a P1dB of about 40dBm. So its working fine.
6cm PA chain output power
The current consumption for the both PA separately (orange driver current in mA, blue PA current in A).
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.
Just for fun i tried to collect some components from the shelf and plugged together a simple monitoring receiver for 9cm.
I have a DF9NP PLL OCXO for 2592.2MHz and a pipe-cap filter tuned to 3400MHz. From China i ordered a wideband LNA some month ago. It has about 15dB gain on 9cm. The mixer is a ZEM-4300+ (+7dBm LO). The setup results in a IF of 807.8MHz which is received with an RTLSDR and the very nice GQRX software.
With a short wire attached to the input of the LNA i was able to receive the local 9cm beacon DM0TUD.
In this post [Link] i wrote about a 6cm horn for offset dishes from Russia. The horn was designed for 5720MHz and i was not able to tune it to 5760MHz were i wanted to use it. DG2DWL gave it another try and added a M6 tuning screw opposite to the feed tip. He managed to get the resonance to the correct frequency.
So with some modification these horns are a good alternative for offset dishes in the 6cm narrow band section.
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.
Please remember the 700C mode uses only 1kHz of bandwidth.
If you are interested in some tests just send me a email to firstname.lastname@example.org
Usually i do not post links to foreign content but here is a really interesting talk by Bruce K6BP on the state of digital voice and open source usage within amateur radio in general.
Thanks a lot to Hamradio Now for making this talk available !
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.
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:
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.