How can I make a simple antenna trimmer?

[sctvguy1]

I have an old boatanchor, a Lafayette HE-10, that takes a single wire
antenna and a ground. I would like to make a simple trimmer to optimize
the 75 feet of random coated wire. The wire is copper, Radio Shack.
Thank you,
Bob Grimes

[Irv Finkleman]

If you mean a simple means of shortening the wire to a resonant
length, simply roll the end of the wire into a ball, no special
winding or anything, just like a ball of twine. This method is
often used as a counterpoise on some of the multiband whips
where a ground is not handy. B&W make one, and so does
MFJ. You can download their manuals and read what I have
just described. I have used a homebrew look-alike
to the B&W AP-10 which uses the same method for the counterpoise
and it worked well. And you don't have to cut the wire. As well,
you can roll or unroll the ball to adjust the length for different
frequencies. In an emergency you just take it off the ground
end and connect it to the antenna -- it works! Simplest and
cheapest antenna system you can imagine!

The ball of extra wire acts like a choke and has no real effect
on anything other than to effectively shorten the wire.

Hope this helps!

Irv VE6BP

[Jeff Liebermann]

On Thu, 5 Nov 2015 02:28:05 -0000 (UTC), sctvguy1
<sctv...@invalid.net> wrote:

>I have an old boatanchor, a Lafayette HE-10,

<https://www.google.com/search?tbm=isch&q=lafayette+he-10>
<http://www.radiomuseum.org/r/lafayette_he_10he1.html>
<https://www.youtube.com/watch?v=Lk1dmQEsoIk>
Made by Kenwood/Trio for Lafayette.

>that takes a single wire
>antenna and a ground. I would like to make a simple trimmer to optimize
>the 75 feet of random coated wire. The wire is copper, Radio Shack.

I can't tell what it uses for an antenna input (50 ohms, 75 ohms, 300
ohms, broadband, narroband, tracking filters, whatever) so I can't
offer an antenna tuner design. Any idea what's behind the antenna
connector?



--
Jeff Liebermann je...@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

[sctvguy1]

On Wed, 04 Nov 2015 20:10:35 -0800, Jeff Liebermann wrote:

> On Thu, 5 Nov 2015 02:28:05 -0000 (UTC), sctvguy1 <sctv...@invalid.net>
> wrote:
>
>>I have an old boatanchor, a Lafayette HE-10,
>
> <https://www.google.com/search?tbm=isch&q=lafayette+he-10>
> <http://www.radiomuseum.org/r/lafayette_he_10he1.html>
> <https://www.youtube.com/watch?v=Lk1dmQEsoIk>
> Made by Kenwood/Trio for Lafayette.
>
>>that takes a single wire antenna and a ground. I would like to make a
>>simple trimmer to optimize the 75 feet of random coated wire. The wire
>>is copper, Radio Shack.
>
> I can't tell what it uses for an antenna input (50 ohms, 75 ohms, 300
> ohms, broadband, narroband, tracking filters, whatever) so I can't offer
> an antenna tuner design. Any idea what's behind the antenna connector?

It is just a simple old screw, made for a copper wire antenna, the radio
was made in the late 50's. I used to have one that I made out of a
variable capacitor and just tuned the knob to trim the antenna. I am now
64 and that was when I was in junior high school? Can I get a variable
capacitor for an old radio and connect the two ends?

[Jeff Liebermann]

On Thu, 5 Nov 2015 04:49:49 -0000 (UTC), sctvguy1

I'm 67 and know the feeling. The lab that I patiently built up over
the last 40 years is now considered a test equipment museum.

Yes. Just a small 365pf(??) or lower value variable capacitor should
work. I wanted to see the circuitry so I could provide a better guess
at the capacitor value. Something like these:
<http://www.ebay.com/sch/i.html?_nkw=365+pf+variable>
Any old tube or xsistor radio should have one. Dig around at thrift
shops or ham flea markets for old radios and junk boxes.

Good luck and I'm amazed that such an old radio still works.

[gareth]

"Jeff Liebermann" <je...@cruzio.com> wrote in message
news:9lql3b532rkaidc3r...@4ax.com...

>
> I'm 67 and know the feeling. The lab that I patiently built up over
> the last 40 years is now considered a test equipment museum.

As for my PAL TV cross-hatch-and-dot generator :-(

[amdx]

And my Boonton 260A Q meter, (mid to late 50's).
Still well functioning though!

Mikek

[sctvguy1]

On Wed, 04 Nov 2015 21:47:18 -0800, Jeff Liebermann wrote:


> Yes. Just a small 365pf(??) or lower value variable capacitor should
> work. I wanted to see the circuitry so I could provide a better guess
> at the capacitor value. Something like these:
> <http://www.ebay.com/sch/i.html?_nkw=365+pf+variable>
> Any old tube or xsistor radio should have one. Dig around at thrift
> shops or ham flea markets for old radios and junk boxes.
>
> Good luck and I'm amazed that such an old radio still works.

I had it recapped and fully restored by an old ham friend. He even wired
it for an Heathkit Q-Multiplier. Really comes alive on the AM band at
night!

[Allodoxaphobia]

On Thu, 5 Nov 2015 07:57:15 -0600, amdx wrote:
> On 11/5/2015 5:06 AM, gareth wrote:

>> "Jeff Liebermann" <je...@cruzio.com> wrote:
>>>
>>> I'm 67 and know the feeling. The lab that I patiently built up over
>>> the last 40 years is now considered a test equipment museum.
>>
>> As for my PAL TV cross-hatch-and-dot generator :-(
>
> And my Boonton 260A Q meter, (mid to late 50's).
> Still well functioning though!

And my WWII-era BC-221 freq meter -- still in use.
Together with my Millen 90651 Grid-Dip Meter -- the 1950 model with
the 955 acorn tube -- still in use.

Jonesy
--
Marvin L Jones | W3DHJ | W3DHJ | http://W3DHJ.net/
Pueblo, Colorado | @ | Jonesy | __
38.238N 104.547W | jonz.net | DM78rf | 73 SK

[Dave Platt]

In article <9lql3b532rkaidc3r...@4ax.com>,

Jeff Liebermann <je...@cruzio.com> wrote:

>>It is just a simple old screw, made for a copper wire antenna, the radio
>>was made in the late 50's. I used to have one that I made out of a
>>variable capacitor and just tuned the knob to trim the antenna. I am now
>>64 and that was when I was in junior high school? Can I get a variable
>>capacitor for an old radio and connect the two ends?
>
>I'm 67 and know the feeling. The lab that I patiently built up over
>the last 40 years is now considered a test equipment museum.
>
>Yes. Just a small 365pf(??) or lower value variable capacitor should
>work. I wanted to see the circuitry so I could provide a better guess
>at the capacitor value. Something like these:
><http://www.ebay.com/sch/i.html?_nkw=365+pf+variable>
>Any old tube or xsistor radio should have one. Dig around at thrift
>shops or ham flea markets for old radios and junk boxes.
>
>Good luck and I'm amazed that such an old radio still works.

There's a manual and schematic for the HE-10 (apparently a
Globe-Trotter 9R-4J) at the BAMA.EDEBRIS.COM site.

It looks as if you can use either an unbalanced random-wire or zep
antenna (connect to A1, jumper A2 to E, and connect E to a good
ground), or a balanced doublet (remove the jumper, connect antenna to
A1 and A2).

In either case, A1 and A2 feed into the front-end preselector, which
has a 2P4T switch (one position per band) connected to four sets of
tuned transformer couplers. The signal goes into the primary of one
transformer, out through the (tuned-per-band?) secondary, and then
goes to the grid of the first tube via a 250 pF cap. One of the
tuning-capacitor gangs is connected to the secondary/gate feed as
well.

[Irv Finkleman]

Oops! I didn't realize what you meant by trimming an antenna.

Irv VE6BP

[Jeff Liebermann]

On Thu, 5 Nov 2015 10:55:37 -0800, dpl...@coop.radagast.org (Dave
Platt) wrote:

>In article <9lql3b532rkaidc3r...@4ax.com>,
>Jeff Liebermann <je...@cruzio.com> wrote:
>
>>>It is just a simple old screw, made for a copper wire antenna, the radio
>>>was made in the late 50's. I used to have one that I made out of a
>>>variable capacitor and just tuned the knob to trim the antenna. I am now
>>>64 and that was when I was in junior high school? Can I get a variable
>>>capacitor for an old radio and connect the two ends?
>>
>>I'm 67 and know the feeling. The lab that I patiently built up over
>>the last 40 years is now considered a test equipment museum.
>>
>>Yes. Just a small 365pf(??) or lower value variable capacitor should
>>work. I wanted to see the circuitry so I could provide a better guess
>>at the capacitor value. Something like these:
>><http://www.ebay.com/sch/i.html?_nkw=365+pf+variable>
>>Any old tube or xsistor radio should have one. Dig around at thrift
>>shops or ham flea markets for old radios and junk boxes.
>>
>>Good luck and I'm amazed that such an old radio still works.

>There's a manual and schematic for the HE-10 (apparently a
>Globe-Trotter 9R-4J) at the BAMA.EDEBRIS.COM site.

Thanks:
<http://bama.edebris.com/download/lafayett/he10/he10.pdf>
<http://bama.edebris.com/download/lafayett/he10/KT-200%20HE-10%209A-4J.pdf>
The latter link shows their recommended antennas on Pg 4. If
connected between A1 and A2, a 1/4 wave dipole should work, which I
would guess would be about 75 ohms input impedance. The other
connects A2 to E(earth) and produces an inverted L or Zep. I can't
squeeze anything useful out the schematic on Pg 7.

>It looks as if you can use either an unbalanced random-wire or zep
>antenna (connect to A1, jumper A2 to E, and connect E to a good
>ground), or a balanced doublet (remove the jumper, connect antenna to
>A1 and A2).

Yup. If the wire is too short, add series inductance. If to long,
add series capacitance. With a low impedance input to the receiver,
an antenna tuner might be better, but hardly worth the effort.

>In either case, A1 and A2 feed into the front-end preselector, which
>has a 2P4T switch (one position per band) connected to four sets of
>tuned transformer couplers. The signal goes into the primary of one
>transformer, out through the (tuned-per-band?) secondary, and then
>goes to the grid of the first tube via a 250 pF cap. One of the
>tuning-capacitor gangs is connected to the secondary/gate feed as
>well.

Yep. I can't guess(tm) the bandwidth of the front end filters without
knowing the turns ratios and approximate inductances. Offhand, it
looks like an equal number of primary and secondary turns, which makes
it a rather low Q affair. Probably needs to be that low to cover the
entire band without a tracking filter.

Gorgeous wiring diagram on Pg 9 and Pg 10. It's even drawn in
perspective. I haven't seen anything that nice if many years.