[nrv-hams] Pass Band Filters

[Carter Craigie]

Hi fellow NRV ARC members,

At last Monday evening's club meeting I introduced, as new business, a plan
for our club to become involved in making 4 pass band filters, expressly
intended to alleviate the interference such as we had at last year at Field
Day (FD). The CW station got into the SSB stations, and vice-versa. We spent
a fair amount of operating time trying to reduce the interference, and were
only somewhat successful. So we're thinking about FD 2012 already! Read on.

Donnie Coleman, AB4I, has a solution, one that has worked in years past:
something called bandpass filters. Basically speaking, if an op is on 80
meters CW, he/she won't even hear the other transmitters (SSB, CW, or DATA)
that are simultaneously operating on any of the other bands.  It would be
like that CW station were the only one there at FD!  And the same would be
true for the other station(s)  as well: the SSB operators would not hear the
CW station on the air, unless then switched to the same band with the CW
station.

This sounds like a really good idea to me, especially as I learned that the
club has used a very similar bandpass filter model before, many years ago,
and it worked.

The idea would be to have club members build four (4) of these filters, so
that, at some time in the future, we might want to go from Class 3A to Class
4A, meaning we'd be having 4 stations running on the air at the same
time--with no interference from each other, so long as we stay on 4
different meter bands. This sounds pretty good to me, and it did to all the
members who were at Monday's meeting.

At the meeting, Donnie spoke about the project, and passed around a sample
of what one of the filters would look like. This was a prototype he had
built, and was done using something called "ugly construction," but it was
enough for all of us to see the ten (10) toroids, each wound with variations
of 1, 2, 3, or 4 windings of wire.

We could also see the capacitors in place, already soldered to the PC board
that Donnie has made, with a rotary switch to select the band.
Indeed, he will make and donate all four of the PC boards and all of the
wire needed to do the winding of the 40 toroids--ten per each bandpass
filter.

Kay and I have already purchased the various parts. So there would be no
expense to the club, and the treasury won't be hit up for any costs. What
WILL be expected, though, is for enough of us club members to come to the
Dublin Fire House on a Saturday morning to do the toroid winding and the
capacitor soldering, and the kit assembling.

This should be a real learning experience for us--and a lot of fun as well.
The winding is not too hard to do, and once you've done one, you'll be
champing at the bit to do more.

Everybody at the club meeting expressed an interest in getting involved, and
that was most heartening! The immediate problem will be finding the date(s)
that enough of us can come to do the work. John C Lawson KJ4NGC assures me
that, given a two-week warning, the Fire Department would allow us to do the
work there, especially if we could come in the morning. By the way, there is
a second-floor meeting room there as well as the one we were in on Monday
night, so he thinks the chances are very good that we could get a Saturday
morning of our choice.

I have volunteered to be the one who finds a date which is suitable for most
of us. This will require some action and commitment from each of you who
wants to be involved in this project. We will first start to ask you to
check your calendars for the months of December and January.

Check with the important people in your life to see if you can spend some
quality time starting on a Saturday morning during this 2-month period.

Then email me (carter128 at verizon.net) the Saturdays in that time frame that
you positively can NOT attend.  I will take an accounting, and try to find
THE Saturday that MOST of us CAN make it. I realize that some people have
obligations they cannot skip, so there will be no hard feelings if you can't
make the first meeting, as there will probably be one or two more
get-togethers before the project is successfully completed. We ought to be
able to find some way you can be involved in this project--and we want you
ALL to take part, if you possibly can.

Donnie says that he has access to some sophisticated equipment where he
works, and he has volunteered to do the final tweaking of the filters for
us, and we thank you for that Donnie.

So, let's get started by sending to me an email with all the Saturdays that
you absolutely, positively CANNOT attend the first construction meeting at
the Dublin Fire House. I work best by using a deadline, so let's say to
write me back by Saturday, December 10th at 12:00 Noon. I hope that will
give everybody time enough to look over their calendars, to check with
church and work and home obligations, to check with bosses and managers
and/or spouses and significant others.

I will get back to everybody on Sunday, December 11th, on the Sunday night
net at 8:00 PM on the 147.180 repeater. (And if my signal is bad, I will
email everybody the following day!)

I hope you all will respond as soon as you can. I promise you that this will
be fun, and educational as well!!!

73,

Carter N3AO