{Collins} Re: 75A-4 AM filters



The new filter will be mounted vertical, so the leads at the top will need to be dressed so that they do no affect performance.  If improperly dressed, they will lead to blow-by and increased bandwidth. I tried the 8 kHz filter and recall I used some low capacitance shielded cable for connecting.  

As for the 9 pin plug, you can make your own using a 9 pin socket.  Remove the metal ring and then insert bare solid wires into the pins.  The diameter should be the same as the pins on a 9 pin tube.  Probably something like #18, but I do not have one handy to measure.  Cut them off at the same length of a tube pin.  Best to solder these new pins in using a small soldering iron - but you should be able to heat the bottom pin and put solder in the top.  When you are done, invert the socket and you have converted it into a plug.  

You can use the S meter and crystal calibrator to manually draw out the shape of the new filter.  If the terminations are not correct, the "flat top" will have holes in it.  Close is good enough for amateur use.

73,  Colin  K7FM 



-----Original Message-----
>From: DW Holtman <future212@xxxxxxxxxxx>
>Sent: Jun 18, 2007 8:09 AM
>To: Collins Reflector List Server <COLLINS@xxxxxxxxxxxxx>
>Subject: {Collins} 75A-4 AM filters
>
>Hello,
>
>Has anyone tried using an 8 KHZ filter out of an R-390A for a wide band 
>AM filter on the 75A-4? I have a good 8 KHZ filter that is sitting in a 
>drawer. Looking at the schematics, it looks like it should work. I read 
>a couple of notes on the archives, but nothing specific.
>
>If anyone has done this, how did you package it? What did you use for 
>the 9 pin tube base, an old tube, broken off?
>
>Has anyone just jumpered the input to the output with a cap for a super 
>wide (15KHZ ?) filter.
>
>Best,
>DW Holtman
>WB7SSN
>
>
>.
>SHARE THE FUN: JOIN THE COLLINS COLLECTORS ASSOCIATION TODAY !
>      http://www.collinsradio.org/html/membership.html    -paypal accepted-
>.
> NETS: Tues & Thur: 3.805 MHz-2000 Central + Fri: 3.895 MHz-2000 Pacific
>  SUNDAYS: 14.263 MHz-2000 UTC  +  AM Net: 29.050 MHz-1200 Central
>       1st Wednesday AM Net 3.880 MHz-2000 local (ET, CT, MT, PT)

.
SHARE THE FUN: JOIN THE COLLINS COLLECTORS ASSOCIATION TODAY !
      http://www.collinsradio.org/html/membership.html    -paypal accepted-
.
 NETS: Tues & Thur: 3.805 MHz-2000 Central + Fri: 3.895 MHz-2000 Pacific
  SUNDAYS: 14.263 MHz-2000 UTC  +  AM Net: 29.050 MHz-1200 Central
       1st Wednesday AM Net 3.880 MHz-2000 local (ET, CT, MT, PT)





This archive was generated by a fusion of Pipermail (Mailman edition) and MHonArc.