Found at Rally: Triplexer.

 A few weeks ago I found this at a local get-together taking place at a repeater site. At this meeting they sell (often donated) stuff for the benefit of running the repeater.

This year I found an unknown set of band filters in a box, I suspected that it would be a kind of triplexer, and toady I got my NanoVNA out, and yes it is.

The connector at the far side is the common one. On the near side we see two very recognizable labels, VHF and UHF. I did not know what the third one was, but measuring I found.

Testing from the common port:

TOS: Low pass filter, flat up to 117MHz, then a small dip of up to 5dB, then a 3dB cut-off at about 134MHz.

VHF: Flat from 135MHz - 270MHz, but some feed through up to about 315MHz. Good attenuation below 100MHz and above 400MHz.

UHF: High pass filter with 3dB cut-off around 336MHz. Attenuation on 1300MHz was about 3dB.

Residual attenuation:

Below 100MHz: Practically flat with <0.5dB attenuation

VHF: <0.5dB at 144MHz

UHF: <0.5dB at 435MHz

Attenuation between band ports was more than 22dB at frequencies where I would expect to transmit, so that is insufficient for a transceiver triplexer. For a VHF-UHF monitoring receiver system, this would work nicely.

I got a few of the filters for experiments. I had decided that the shielded boxes, at least, could be useful for other RF projects, and there were some decent looking (SMD) capacitors for VHF and UHF. There were quite a bit of these filters,  so I might have got a few more. If they are there next year I may get some of them again.

 Yes, finally I got to use my RF test equipment, now it is time to get some construction done.

Quick Experiment With the LO Module and Some Chinese Modules. 2.4GHz signal achieved.

 Today I got a quick set-up to see how some of the modules I have could be used as a transverter or up-converter from 432MHz to 2400MHz.

Here are the parts:

- the 2009MHz oscillator module I tested a few days ago

- a mixer PCB module, IF DC-1.5GHz, RF/LO 1.5-4.5GHz

- a 2.4GHz filter PCB module using "hairpin" resonators

- a Wilkinson combiner/divider hybrid PCB module

All this was just lying loose on the lab desk, connected with SMA cables with the first port to the 35-4400MHz spectrum analyzer and the second port of the hybrid terminated with a 50 Ohm load. The second port is intended for use in 2.4GHZ reception

For the test I set my signal generator to a 391MHz IF, mixing with 2009MHz to get 2400MHz out.

The raw signal out of the mixer was as expected, a bit of 2009MHz LO feed through with LO +/- IF signals about 30dB stronger

Adding the filter (and the hybrid) provided a solid signal on 2400MHz. The LO signal was about 45dB down, and the image frequency was about 55dB down.

The results are encouraging. I would expect the stray LO and image signals would be better attenuated when the mixer/filter/hybrid  modules are mounted in a shielded casing, but for the transmitter path I intend to mount a second filter between some of the amplifier stages, in a second shielded casing.

For a receive path in a transverter A second filter is probably also a good idea, but at present it may not be necessary. In principle this is a very low powered and very insensitive 391/2400MHz transverter.

What comes next (in no particular order)?

- modifying the LO module to generate 1968MHz, so a 432MHz  can be used as the IF.

- building an amplifier chain, so I can get a minimum of about 500-800mW output.

- building the modules into shielded casings Except the LO, it is already in an excellent shielded box.

- Start mounting this arrangement into a sufficiently large casing

- adding circuitry for supplying and controlling the LNB used for QO100 reception. Right now the QO100 set-up has separate transmitter and receiver.

- adding receive amplification/filtering for 2.4GHz.

- adding control circuits, such as T/R switching, band switching etc.

- adding a second down converter, so the LNB's IF signal can be received on 144 or 139MHz

- maybe a bit more when I can think of it.

Pipe Caps Received. Filters for 2.4 and 10 GHz.

I am just back from some non ham radio related travels.
I have received some copper pipe caps, suitable for making simple filters for the 2.4GHz and 10GHz bands, and a length of semi-rigid coax cable.
On the way: 2009MHz LO modules, can be modified for 1968MHz (2400MHz TVTR LO for 432MHz IF) or possibly 1960MHz  (for 439MHz IF) with an added PLL or DDS in place of the internal XO.

I have been reading up on articles about those filters, and it looks possible, even with my not too good skills in mechanical construction, to make a few filters.

Finally, I also found a filter with a centre frequency of 2375MHz and bandwidth of close to 300MHz. This could be suitable for a transverter with 432/439MHz etc IF. I knew I had it, but could not find it before, due to the mess of moving.

The equipment necessary to test the filters for 2,4GHz filters I have. It is the MiniVNA vector network analyzers, covering all bands from a few 10s of kHz to 3GHz.

For the 10GHz filters I will have to rely on a simple signal generator like the HB100 radar module, possibly modified, and a microwave uW/mW meter.
A friend had made one with about 60-70dB range, and I intend to use that. It only provides a simple tuning aid, but I think I can get access to some better test equipment at a local ham with an extensive set of test equipment, for better alignment of filters.

Things are slowly starting moving.

The Last Ingredient Necessary for a 2.4GHz Transverter Has Arrived.

Today I received some Polyimide tape from China. This should make it possible to lower the resonant frequency of Microstrip and Stripline filters, applying the tape to the resonators.
This should increase the dielectric constant of the surroundings of the resonator strips, thereby lowering the velocity factor , effectively electrically lengthening the resonators.

I have seen this tape used in a TV satellite LNB for lowering the band pass filter frequency. My question is how much loss, (i.e. lower Q) this adds to the filter.

I was promised some PTFE (Teflon) tape from a friend (I suspect with lower losses), but we have not yet had time to get it to me. He has some stuff that I can measure, so he wants to come here, and bring the tape.

The coming week end will be quite busy, but after that I should be able to test the tape for losses, and frequency change of the filters I already have.