2m Station Progress

Three months ago, a nice, clean 2m Microset 200W amplifier was advertised on a Facebook ham radio page.  With lots of money to spend on the house and kids, I struck an agreement with the seller to pay for this non-essential amp over three months.

The new arrival, together with its tidily homebrewed cooling fans.

Yesterday, the amp duly arrived!  In as-new condition, this was a good £200 cheaper than a new model.

This is the first time I've ever used an amplifier, so there is a little learning to get to grips with - not least whether a 25A continuous PSU would be adequate to power it (it is).   In general, it will have no use other than when there is unusual DX available via tropo and/or Es.

One issue that is common to all these amps is a momentary spike in SWR when using RF to trigger the amp.

I was fortunate that Jim, GM4FVM, helped me with his experience, advising that a wired PTT to the amp is better, and avoids this problem.

In practice, with careful adjustment of the output, ALC and audio levels, it's possible to reduce the spike to about 1.5:1, and it only lasts for a fraction of a second.  Jim says that it's crucial not to have the amp's receive preamp turned on if using RF triggering, as the SWR spike will eventually destroy it.

I've now wired the PTT on the amp, and Jim's advice is sound: the SWR spike is completely eliminated.  If you have one of these amps, just connect the lower pin, labelled, confusingly, '-', to the rig's PTT line (if that socket on the rig is already occupied and you don't want to disrupt your existing system, then you can, for example, strip some of the connecting wire back, and attach your amp PTT wire there - solder or any form of clip is fine.  The other, '+' pin you connect to the rig's ground.  That's all there is to it.  

The 8-ele beaming east at sunrise.

Nevertheless, I did get the amp up and running, and managed three QSOs with very strong signal reports of around -04dB, on an evening when there was no particular 2m propagation.  This, with the antenna in its lowered, wind-safe position of just 2m above ground!  As the map below shows, the signal from my east-pointing 8-ele beam was getting to most parts of the UK.

The wider message here for newcomers is that, with a little application of wisdom and care, used equipment can provide you with years of enjoyment.  I have only once bought a new transceiver.  Almost every other piece of equipment I have is used, and never caused me any problems.