Es’Hail -2 on 2m

I’m currently working on a 739MHz to 145MHz down converter so that I will be able to hear downlink signals on my 2m band transceiver.

432MHz will  be used to drive the 2.4GHz uplink transverter/PA/antenna. A dual band, ‘satellite’ transceiver can then be used on Es’Hail-2 in full duplex mode.  The propagation delay will make sending CW and voice difficult, but at least you will know you are getting in and not qrm’ing someone else.

As PA5Y has pointed out, the latency of the typical SDR would make this even worse, suggesting an analogue receiver might just be preferable!

The downconverter is based on my Iceni transverter board, receive section and LO, with 99MHz (lockable) crystal oscillator. I’m using a up mspare (redundant) Iceni V1.0 PCB.

The first problem is that the original LO could not be persuaded to generate any worthwhile power on 594MHz (739-145MHz). Instead I opted to tune it up to half frequency (297MHz) and try using  sub-harmonic mixing. After a lot of work I am achieving a conversion loss of about 20dB through the mixer in this mode.

With a 735MHz Toko helical filter (tuned to 739MHz) on the RF input and suitable filtering/ mismatching on the IF to try  and ensure that the mixer was seeing unwanted frequencies reflected back in the correct phase to minimise conversion loss, i was able to add a post mixer amplifier and filter to achieve  an overall insertion gain of -10dB. As the LNB has massive gain, the downconverter noise figure is not critical.

I have more work to do on the converter before I am happy with it. More anon.

I subsequently found that the level of noise from the LNB, down at 739MHz, was considerably down compared to at 1GHz. Consequently my plan to add a passive three way splitter after the bias tee feeding the LNB resulted in a poor overall system noise figure when feeding the downconverter. I may have to add the PSA4-5043 RF stage back into the Iceni-based downconverter....

Sam

More on Es’Hail-2 sat.

After seeing today’s excellent test signals in the satellite amateur transponder passband I was motivated to dig out my 13cm SG Labs transvreter and fire it up. It hasn’t been touched in two years and never previously fired up on 2400.050MHz. That’s the start of the 250kHz narrowband uplink range, extending to 2400.300MHz.

After initial tests, using my FT817 on 432MHz, and checking all was well on my spectrum analyser I thought it might be interesting to see just what 432MHz drive levels I could use and still get useful output from the transverter. The reasoning being I wanted to use an Iceni 70cm transverter with my K3 as the drive source. I wanted, if possible, to use the Iceni barefoot i.e. no add on 70cm linear amplifier. The SG Labs transverter can stand several watts of 70cm drive, but the barefoot Iceni only generates 50mW.

I first tested with various levels with my SMG Signal generator set to 0dBm, transverter input attenuator set to minimum loss. The transverter gave +7.5dBm output. The RF Vox did not operate. As I don’t require this facility, no problem. Increasing the drive to +10dBm gave +18dBm transverter output. Finally, with +16dBm drive, the SG Labs gave +25dBm output. RF Vox worked from +10dBm upwards.

The transverter will be mounted in the shack and a coax cable will connect to the 25W output GaAs FET PA out by the transmit antenna.  The  power amplifier requires about +10dBm at 2401MHz (wideband PA) for full (saturated) output and that gives lots of room for both coax loss and an attenuator at the PA input!

It looks feasible to use the Iceni barefoot  in this application.

Of course, underdriving the transverter will result in the spurious outputs (image and any Residual LO) as well as the transmitted composite noise being effectively 10dB below spec. However with a 432MHz IF these are a long way down.

Now to box the transverter and arrange for somewhere for it to mount in the rack.

Sam

Transverters

Yesterday I announced on my web page, and in a couple of reflector messages, that I would no longer be producing transverter kits. These have proven to be very time consuming to produce, to the detriment of my involvement in the hobby. Added to that the stock handling and holding is a pain, although the whole excercise has been interesting and shown there is still a demand for this type of radio equipment. VHF and up SDR radios have not taken over entirely!

I am in discussion with a well known and established company to take over producing the transverter kits, but it is early days and no guarantee it will happen. The economics may well rule it out.

I still have stocks of many transverter parts, but I will not be putting these into full kits; instead I will make them available as parts only to anyone wanting to build an  Iceni or Anglian transverter, prior to having a new supplier. After that it will depend on my agreement with the new owner.

I am no longer arranging to hold new stocks of the WA5VJB PCB antennas. Again, I still have existing stocks of these antennas to sell. Although not a particularly time consuming part of my kit business, arranging to acquire adequate stock of some antennas can sometimes be frustrating.

I will continue to produce my VLNA and PGA low noise preamp kits. These are far less time consuming to produce!

Sam