Sunday, 18 October 2015

The Agony of Choice

So, ive received a quote for a pair of custom ground crystals to get my Pye PF8 running on 70cm. This was never going to be a cheap option! Im not going into pricing specifics but suffice to say that the cost of a Tx/Rx crystal pair for one channel is about that of a Chinese dual band low end handheld of the UV-5 type! Of course, I always knew this would be the sticking point, so I do have feelers out hunting down a spare channel pair hopefully in someones junkbox that they would be happy to let go.

Crystals for the PF8 are of the HC45/u variety. These are reduced height varients of the HC18/u, as shown above. These are very small when compared to the FT243 WW2 vintage rocks! The HC-6/u crystals above are the size that would be needed to convert similar 1960's/70's era mobile sets such as the Pye Westminster. Nowadays of course, such things can be done with off the shelf Direct Digital Synthesis modules! But, theres no space in a PF8 for such things! So, single rock-bound channel it is!

I received today the above book - 'Surplus 2-way Radio Conversion Handbook' by Chris Lorek. This is a must for anyone with a fancy to refurbish and convert these old radios. It details the conversion of the PF8 plus many more, including the quite unusual PF9 - a reversion to the old PF1 Tx/Rx separates style! It seems some users just couldnt get used to an 'all in one' handheld radio!

Tx Xtal
Rx Xtal

So, unless someone finds and offers me a channel crystal pair, i'll have to fork out for a custom job. Which leaves me with a dilemma - which channel to choose? This is not a choice to be made lightly at these prices! I want a simplex channel, since I dont wish to be tied to a local repeater, nor to have to add a CTCSS unit! But which one? Theres effectively eight to choose from, between 433.400MHz and 433.575MHz in 25kHz steps. 433.550MHz is often used, as is 145.550MHz a band lower, for rally talk-in stations. Now, admittedly fewer rallies offer this facility these days with the advent of in-car satnav and smartphones running Google Maps, but since plodding around rallies and events if where im most likely to use the PF8, its probably still best to avoid this channel.

So that leaves seven to choose from. I could of course put it on 433.500, the calling frequency. That will allow me to hear calls, reply, etc, but not to hang about and natter. I could go then to one of the other frequencies where I would be free to ragchew, but unless previously notified or announced, no one would know to call me there, and of course, if its occupied at the time...

If I do select a discrete channel, then which one? Either side of the calling channel would seem the best option, but these do tend to become occupied soonest, but the further out frequencies, whilst likely to be clearer, mean its less likely that I would just be stumbled on by people having a quick tune around, for instance if I decide to try the PF8 out on SOTA.

Im leaning toward 433.500 MHz if im honest. At least on the calling channel i'll find some activity!

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