Is anyone running a Dressler EVV700 Gaas fet mast head pre-amp on 432?
I have one with a dead device. I have found a poor copy of the circuit. Two different circuits actually, but cannot identify either of the devices from the circuit.
hi Kevin.
the active device is shown on page 3 at the bottom GaAsFET CF300C.
i was aware that there is no mud map or parts list.
i have a pet parts supplier i will check to see if the fet is available.
yes it is available Kevin info on the email i have sent to you.
Gordon VK5KAA
Last edited by VK5KAA on Sun Apr 22, 2012 10:48 am, edited 1 time in total.
KJ,
is it a 3SK97 dual gate FET in there? I had a pair of these (2 & 70) a long time ago and I think the equiv for what was in there from Europe was a 3SK97, which is not outstanding by todays standards but quite usable. Anyway that might get you started if the original is dead.
Have a dressler knock off here for 2mx (no case but has relays) that was built by a VK6 and it has a 3SK93 in it (markings on the case of the FET are all but rubbed off).
The CF300 was used in ye olde VK5 70 cm pre-amp kit. If you wanted to get it going again with a CF300, it might be worthwhile contacted Mark VK5AVQ and seeing if he still has spare stock from the old ESC hoard. Otherwise I bought a couple from him as spares a few years ago, but I'm not using the pre-amp any more (I may have toasted it...), so at a pinch I have one in my spares draw that I could live without.
I'm using a newer pre-amp with an ATF54143 these days - the one from AR mag a couple of years ago.
Hi,
I have a Dressler from the mid 80's EVV700 GaAsfet, which I got from a ham in the UK, when I lived there (in the 70s to mid 80's).
He blew up the RF device a few times (CF300 from memory), and I found out that he was blipping the PTT and I suspect a RF spike was popping the device. I remember doing a mod to the sequencer box, so one of the time constants reset quickly when going off TX.
( He was probably running 150 to 250w PEP)
Noise figure was around 1.1/1.2 dB from memory
Hi
I found the info for my earlier unit online (single stage Dualgate GaAsfet) and it said it was the 3SK97. So I was probably using those. However I did have a play with some CF900 fets during the 80's.
I found the LNA, but am still looking for the control unit.
Kevin
