9cm (3400MHz)

Link to GM4ISM GM4LBV Personal Beacon news

Link to EME activity


GM4ISM home and Portable 9cm equipment

Equipment for 9cm is an old DEM single board transverter retuned from 3456MHz to 3400MHz.

Power is raised to 600mW in a further 3 stages, Preamp using FHX05 is under construction.


Portable equipment and operation

My portable station now (March 05) comprises the DEM single board transverter + integral 600mW PA, and a PA / preamp system built around Ionica bits.

The Ionica PA (unmodified) gives 15W, I have cut the front end stages from an RX block for a preamp, and chopped one of the pin diode attenuator sections from the base station motherboard to give me a 10-30dB variable attenuator for the power amp input. The whole lot runs from 12V, as the -12V is generated by an inverter (see the PA mod page), and this also allows the use of a 28V coax relay. as a simple indicator of TX op power I have used the inbuilt RF detector output to drive a LED via 270Ohm resistor. Brightness varies with output power.

QSOs G3XDY at 470km via aircraft scatter from a portable location near Gatehouse of Fleet, Dumfries and Galloway,

G3UKV first GI to G @279 Km (Tropo) GM4LBV first GI to GM (tropo) G3XDY at 535km via aircraft, scatter from a portable location near Kilkeel Co. Down


The antenna was an 80cm sat TV dish with a simple flared tin-can feed.


mini DXpedition to Jersey 11-13th October from IN89WG 2 QSOs on 9cm, G4ALY first GJ to G and G3XDY (390km)

using the same equipment but with a 6" square patch antenna from Airspan equipment shown below with the 3cm transverter and dish, overlooking St Hellier

9cm patch antenna alongside the 3cm system sample QSL card




I had planned to use 3 of the Ionica PA units combined to give about 50W for home (EME) use, though I have now obtained a single Toshiba power amp (Thanks to John GM4LBV) that will do that job without the hassle of a power combiner.

9cm portable external view portable 9cm amplifier inside


Ionica Equipment

Ionica Base Station Power amplifier.

These are 4 stage, using 'normal' FETs for the first 3 stages, and an internally matched device as the final stage.They work on the amateur bands 3400 MHz to 3456 MHz without modification. Less than 1mW drive is required for about 15W output.

PA output device is a TIM3742 -16 nominal 18W out (42.5dBm) 3.6 GHz to 4.2GHz. Other Units use the MGFC42V3436 Spec'd at 42.5dBm 3.4 to 3.6GHz and a HP device (no data) Ionica PA circuit boards are identical for all units seen to date.

In Feb 01 I had 20W saturated op on 3400 MHz from one of the Ionica amplifiers (modified). I had to manualy bias each device, but no other modification was required. The amplifiers have been used on the 3456 MHz sement of the band without problems

Unmodified, using the on board bias control, the devices are run in a constant current mode designed for class A operation. Only 4A is allowed into the final device, limiting the op power in an unmodified state to about 14W.. but less than 0dBm drive! The beacon near Dundee ran for almost a year continuously with an unmodified Ionica amplifier. It was switched off due to RF hazard concerns, but has been re-located at GM4LBV's QTH on the coast near Montrose

See the PA Use & Modifications page

Some detail of the experenental matching changes to the first 3 stages to allow operation on 2.3GHz.. I have got 2.5W out for 1mW drive, the PA device has proved difficult, as there is very little room to put tuning tabs on the board. These are for guidance only, you may have to tweak the matching to acheive the same results.

I have also done some work on the receive converter which is found in the Ionica base station mast head units. This can be modified quite easily for use on the amateur bands with very reasonable performance.

See the Receive converter page

Adam G0ORY has been doing things with Ionica Consumer units (mainly on 13cm) and now base stations, and is working on a webpage


  PA block ( 1 of 3 to be combined for EME)

Large image 308 Kb





More of the Ionica base station gear is here (some are thumbnails, click to see larger image)



Full size is 206kB

Ionica antennas (Horizontal poln Version)

  some of these antennas are in use at GB3MHX  



NEWS! September 03, the 9 cm beacon is QRV again from IO86RQ with the callsign GM4LBV/B on 3400.068 MHz

Last checked 18th Mar 2007 Frequency 3400.058 MHz seems to have aged a little!


Pictured below is the 9cm Beacon and its antenna at GM4LBV's QTH

Call was formally GM4ISM/B QRT in June 02 due to RF hazard concerns

Antenna 120 ETN 120 Deg Beamwidth 14dBi


3.4 GHz Beacon antenna in IO86RQ
Beacon transmitter, 3400.054, 14W op

3400 MHz EME

Pictures below!

May 2008 work started on EME system

progress as of 24/5/08 Septum feed (with flare suitable for my dish with 4.5 f/D) completed

Measured parameters for the feed in iosolation. RX return loss @ 3400 MHz 32dB, TX return loss 28dB

Cross Polar isolation 29dB

Update Friday 6 June. Power amp has been soaktested on the bench. steady 42W available.

All that remains is to attach the PA to the dish, wire up the ptt system and operate....

Update from the activity weekend 7th and 8th June 2008

On Saturday, some minor bugs and family commitments caused a late start, but once I had the dish pointed at the moon, I was pleased to see a little moon
noise. (about 0.1dB now I have measured it as best I can) This was just enough to aide tracking, though very easy to miss. My tracking system has no
feedback into the shack.. effectively I have AZ and El control, optical tracking when it is clear, and a practiced knowledge of the speed of the
actuators, such that I was able to stay on the moon most of the time. Room for improvement though it must be said, a lot of effort went into keeping on
the moon.. I could make it easier for myself HI
Heard on Saturday were OK1CA at M , G3LTF at T copy, W5LUA O- M other signals heard not identified. signals definitely degraded as the evening progressed.
VE6TA was detectable only on Winrad, far to weak to read any CW, though I suspect QRSS would have been viable, the trace was clearly visible and
reasonably constant. No QSOs resulted on Saturday, though several people reported some marginal copy of my signals.

Sunday, a minor tweak to the preamp gained a little lower noise figure, but not much. Sun noise now 7.2dB
Conditions seemed better though, and I completed with G3LTF fairly easily.. not strong, but good M copy. (the only QSO that is not a country First HI)
OK1KIR was good copy O much of the time, but was struggling to hear me.. a couple of periods he sent almost nothing but M report, and I responded in
kind with my RO report . Finally I got rogers.. Hard going but worth the effort. This is probably a first GM to OK on 9cm
A test with Al W5LUA resulted in a lot of T reports clearly heard.. not very encouraging, then suddenly Al was able to hear me better and the QSO
completed.. #3 in the bag. A good report from F2TU was obtained later, and finally a very easy QSO with Willi LX1DB OO. RST reports exchanged Willi was 539, and I got 449 back.


From these contacts I seem to be hearing about the same level as I am being heard. This ties in with the performance of my preamp which is as far as I can tell about 0.5dB nf
It is obvious though that the dish is not delivering the expected gain, and thus I will need to do some work on the feed.

After removing the flare, the illumination of the dish is more uniform, though overspill seem to be degrading the noise performance. Overall on receive I have not seen an improvement, but I may be louder.

Recently I have worked RW1AW on random about 1 hour befor an arranged sked (a very fine signal, Alex came staright back when I answered his CQ, 529 539 exchanged)

A first GM to Russia on 9cm too HI... Initial #5

Worked LX1DB again a few days after Alex, though with the moon low in the sky and nearer apogee and near the sun the signals were not so good.



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