Yet another 2m 70cm Diplexer.
I recently purchased an Elk log periodic dual band aerial for portable satellite operating.
Unlike the Arrow, it only has a single feed connector and since I use an FT-290 on TX with
a TR-851E on RX I needed a duplexer.
While the aerial is designed for dual band FM handhelds, using a single connector, using two
rigs for CW operating poses a slight problem so to operate full duplex a diplexer is necessary.
Building the diplexer should be quite straightforward by perusing the 'pretty' pictures.
(OK, maybe not so pretty ... they were taken with an 'El Cheapo' tatty phone camera).
A couple of bits of coax, series-resonant traps and 3 x connectors in a home brew
aluminium box and you're good to go.
The box is made from the aluminium cooking tray that was previously 'at home' in the
electric oven ... and you ask me why I'm divorced?.
I used Eirie type ceramic trimmers in case I should ever get the urge to use *MASSIVE*
power like one complete watt. Seriously, I used them because they were in the junque-box,
even though they are quality-wise a bit overkill for this project. (They're microwave trimmers).
The coils were wound with 1mm soft drawn enammelled copper wire 'borrowed' from an RF
choke in a 'dead' power supply ... (well, it's dead now!).
The N-connectors came from ... you don't! want to know. The SO-239 came from a non-
functioning SWeaR meter.
(Non-functioning because it was 'liberated' previouskly, for parts).
The RG-58 C/U coax was a patch lead that 'paid the price'.
The 'loss' of a quarter wave RG-58 at 2m is INSIGNIFICANT - (and I run milliwatts) - but if
you want to split hairs, by all means use higher quality coax.
73 John. <la2qaa@amsat.org>
