Tommy aldermant at alltel.net
Sun Aug 7 12:30:42 EDT 2005


The +12vdc to J5, I would suggest you pick up the 
way Inrad recommends as it is a permanent dc 
voltage for the relay K1. What I did is ignore 
the cutting and splicing of wires for both J3 and 
J4. I left J4 with no connections. If you take 
the bottom cover off the Plus and have the rig 
upside down, with the front facing you, you will 
see the little PC board on your right, where the 
voltages for the PROC switch is located. I ran a 
single wire from the filter board J3 (you can put 
it on one or both pins) through the bottom of the 
wiring harness and up front to where the PC board 
is located and just solder it to the right most 
pin on that PC board. I set S1 - 1&2 to ON and Si- 3 &4 OFF.

This way, you maintain full use of the filter 
selection buttons and can turn the roofing filter 
ON/OFF independent of filter selection. To me, 
this was an excellent idea that K1FK had, but it 
can be easily changed so you dont interfere with the processor button.

What you have in mind certainly should work, 
anywhere you could pick up a positive switched DC 
voltage. From J3, this voltage goes through a 
steering diode and into two 4.7k resistors, the 
junction of the two 4.7k resistors is tied to the 
base of an NPN, 2N3904 transistor, which has the 
relay in it's collector. So you just need enough 
positive DC voltage to turn on the that 
transistor when you want to enable the roofing 
filter. The emitter of the 2N3904 is tied to 
ground, so you would only need something like 
0.6vdc at the divider to turn that transistor ON.

Since I don't use the MAIN/AUX antenna switch 
either, I had thought about connecting to that 
point, but the PROC switch was just so 
convenient. Your other choice of the VOICE switch 
would be another good spot, as that switch is not 
used here either. I do find for normal operation, 
the roofing filter is so effective, that I tend 
to keep it turned on all of the time.

Tommy - W4BQF

At Sunday 11:46 AM 8/7/2005, you wrote:

>Tommy and Dave-
>What I have in mind is identifying a button I don't use, disconnecting
>it from its intended circuit, and using it to switch the roofing filter.
>It doesn't have to be the FM or VOICE buttons. I don't want to use PROC
>since I occasionally use it.
>For example, I will probably never again use an auxiliary receive
>antenna. I could disconnect the ANT switch and solder the MAIN antenna
>permanently in the circuit. Then use the ANT pushbutton to switch in
>13.5 v from somewhere, such as the Aux 13.5v jack on the rear panel.
>This switch would connect to J5 on the roofing filter board.
>Tommy, when you used the PROC button for this, how did you set the four
>switches on S1 of the roofing filter board?
>Thanks for the suggestions.
>                         Jim  N4AL
>Tommy wrote:
> > Jim,
> >
> > You don't actually disable the processor, you basically 'steal' a
> > positive voltage from the pc board for the PROC switch.  The reason I
> > used the PROC switch is only because I very seldom operate SSB. If
> > you do use SSB and the processor, this is probably not where you want
> > to switch the filter on/off. You need just a few milliamps of
> > positive current to turn on the transistor that switches in the
> > roofing filter relay.
> >
> > This idea, which really simplifies then roofing filter installation,
> > was originated and shared by K1FK.
> >
> > Tommy - W4BQF
> >
>The FM and VOICE buttons (nor any other button on the main keypad)
>CANNOT be used directly for this function.  They have a different logic
>interface with the main µProcessor and would require a buffer in order
>to drive another load, such as the Inrad roofing filter mod.
>73, Dave, K1FK
>Fort Kent., ME
>ARRL Life Member
>TenTec mailing list
>TenTec at contesting.com

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