Jan 28, 2009

Receving splitter

W8JI 'Magic T Combiner/Splitter

For feeding the RX inputs of both my Elecraft K2 and TenTec Orion with the same RX antenna, I'm in need for an antenna splitter.
Tom has great information on this subject on his website at http://www.w8ji.com/combiner_and_splitters.htm

I have choosen the design with the 2:1 step-down transformer and the T-combiner using the proposed type 73 binocular ferrites and some thin teflon coated silverwire I have in my junkbox.

Don't forget the 100 Ohm resistor as I did initially, or you end up with a miserable port-to-port isolation!
Measurements show a port 1 to port 2 isolation (and vice versa) of 26dB at 1820KHz.
I'll be using this splitter for the lowbands, mainly 160m so this will be sufficient.

Antenna connectors in your system; TRX vs RX only
Since my home setup is becoming larger, now that I have more antennas put up, I figured it would be a good idea to make a decision on using a different standard connector for all RX antenna wiring in my shack. You don't want to end up accidently transmitting into an RX antenna, or RX input of any rig.
There are currently 3 popular RX connector types:

F-connector; commonly used in the USA in combination with the cheap available RG6 coax
Cinch-connector; used as RX antenna input on most transceivers
BNC- connector; professional and reliable, used on transverters and Elecraft transceivers

Discussing with Rens/PA3FGA, with whom I do a lot of ham experiments, we decided to use BNC from now on only. I had some available as you can see, but there's certainly two items on the list for the next HAM flea-market :)

RX patch-box with common mode filter
Now is a good time to remove the bunch of heavy coax and stuff from the back of my Orion and create a separate 'patch panel' setup with a coax common mode filter. The coax is 2.5mm RG316 Teflon type. The ferrite core is an FT150A-J (#75).

If you look carefully you will see I missed something in the whole process. Anyone noticed this ?

The new RX patch panel board
No big deal yet, but it's a start.

Does it work?
Sure it works fb!
The Orion is true king in reception on 160m. However, the K2 is in its own league, especially when using the analogue audio peaking filter.
In just 30 minutes I heard 5x JA
and 1x USA on my short 20ft reference vertical. At 22:30 UTC that is. Conditions on 160m are simply marvellous these these days

Future wishes?
Yes, I want another one for field day use. And another for splitting the RX output of my 144Mhz transverter. That is on 28Mhz where the above splitter shows only 15dB port isolation. So I will need to carefully design a different splitter using a more suitable ferrite, like #43 or so.