Gang, I received a lot of replies to the Tuner Survey, particularly in the
Home Brew category. (The HBs which copied a commercial or popular design
are listed in a separate post)
It was interesting to see that many of the guys whom we would recognize as
knowledgeable in the ways of RF designed their own matching networks as well
as (or instead of) using commercial tuners.
Don't know how to summarize them without losing some important info, so here
are most of the HB tuners, described in the Brewers own words soapbox style.
They are in no particular order, just as I received them. Since this was a
survey which are usually anonymous, names are not included. However, I'm
sure that these guys would provide more detailed info to those who want it.
Just tell me what you want info about and I'll pass your request on to the
right guy.
1. What is your favorite tuner brand and model no.?
MFJ-949 with some rework by yours truly. Is it a "Pi-Match" (C-L-C, L in
series) It is a Pi-section filter.
2. it is a switchable L (L-C) or T (L-C-L), remotely controlled.
It has all the remote antenna switching too. C is variable from
small to 800 pF; the L's are about 30 uH rotary inductors, largest
I have ever seen. Easily loads anything I have on 160-15. I've
never tried 10, think maybe too much stray cap for that band. It
weighs over 100 pounds including the very heavy weatherproof box.
Including the feedline of 20' RG-8, I measure 0.6 dB loss into a series
R-L or R-C load, with R a precision 50 ohm resistor and Xc
and Xl 500 ohms. (This was measured on 10.1 mHz; I rarely use 20
and up.) I have no idea how it performs when feeding other R's,
but my longwires are never low R.
I do have a high power transformer to step up very low R loads;
tested it to load a 15' whip on 80 and 160, which the tuner could do,
but never used it. This thing is made from a surplus Harris military
tuner I got from Paul.
3. I've built two of these:
http://www.frii.com/~michael/electronics.html
I use a rain gutter at home and this T-tuner
can do just about anything from 3.5MHz to
30Mhz.
The one at work is housed in a Radio Shack
blue plastic box: 6"x3"x2" and tunes a
40m dipole for 80m, 40m and 30m without
any problem at all. It has a little trouble
with 20m on the 40m dipole but I don't
like 20 anyway.
4. A hb link coupler for 80, 40 and 30.
5. One QRO hombrew/w roller coil and
ganged dual capacitors being torn apart for re-building.
6.
A. Home Brew SPC for 20-10 meters (C-L-splitC [one side across coil])
Tee. Uses 50 pF Cin, 50-50 pF Cout, and 6 microH roller L.
B. Home Brew L-C-L Tee using 2 10 microH roller Ls and a combination
(switched)
100 pF, dual 500 C parallel combo C.
C. (Under construction): L-C-L Tee, with switched toroid Ls and 500 pf
parallel receiving C, built into rig and optimized for 30
meters--switchable into an L (series)-C(parallel) L circuit for long
wires.
D. (In planning stage): balanced PI (C-L|L-C) with balun input and
ganged roller Ls (need to find these). Projected values: Cin 500 pF with
switched fixed Cs, 2-10 microH roller Ls, and 500 pF Cout.
E. (In planning): "old fashioned" inductively coupled ATU.
7. What is your favorite tuner brand and model no.?
Homebrew. Is it a "Pi-Match" (C-L-C, L in series)
Yes! Seems to work great! (160-15m)
8. Also use a HB LC tuner for end-fed wires.
9. I use a homemade L- network. The inductor is a 25 Uh max
roller-coil with ceramic form. The cap at the output to ground looks
like 250 pF max. It will load any number of wire lengths
from 1.6-30 Mhz, ham and non-ham.
10. Well, the HB ATU works a little better, in that I can almost
always match stuff. But I know also that it is lossy. It is an old
design re-submitted by Doug DeMaw some years back, and I think reprinted in
QRP Classics.
It uses a link coupling to a parallel-tuned circuit, and a capacitor from
the top of that LC tank goes to the output. Two different coils, shunted
or not by two other coils, allows 80-10 coverage. A resistance bridge is
built in for tuning up. I think the losses come from inadequate spacing
between coils and other stuff in the box
(It's sorta free form in there), and the coils are merely 18 gauge wire
wound on discarded syringe containers (some kind of thermoplastic)-
about 1.25 and .75" in diam for the two coils. Someday I will re-build
and use torroids. I'm sure I'll get better efficiency.
11. W1FB - Simple Resonant Antenna Tuner - home built
12. Not trying to be snide, but I use no tuner. I try to make all my
antenna's resonant at the frequency that they'll be employed on. I try,
anyway!
13. I have four homebrew Pi-Net tuners that have tapped inductors and five
banks each of relay-selected varicaps (that's a total of 40 varicaps!).
These track automatically with the band setting on either of my Omni VI
transceivers. I have a primary and backup antenna for each of my
transceivers, and all antennas are multiband Zepps that are 1:1 SWR on any
five selected bands (which can be determined through jumpers on my interface
board).
I can change bands using either the computer, or the individual bandswitch
on either transceiver. I guess you could say that I've managed to assemble
my "dream station" and, quite modestly speaking, it kicks butt!! I can very
quickly bring either or both transceivers to a pileup and have the advantage
of being able to choose from any of four different antennas, all of which
work quite well, even though they are low wires.
14. One Homebrew BIG/ roller inductor and ganged 365mU Caps, not in use.
15. Both my ATUs are home-brew.
In the shack I use an L-section with switchable capacitor and a
30 uH home-brew roller-inductor. The configuration can be turned
around with a switch.
My portable QRP station uses a pi-circuit made of two 3-gang
500 pF variables (ex fire-bottle receiver) and a tapped inductor
wound on an Amidon T-200-2 torroid.
16. Have a homebrew Ultimate Transmatch from the old ARRL handbook
(SPC backwards).......
17. home brew qrp ultimate tuner split stator input, toroid coil, series
cap out. balun also for tuned feeders, as well as coax input.
qrp series inductor (toroid) series cap (365)
building a manual version of AT-11 using fixed caps and fixed inductors.
18. I've tried L networks and Pi nets. All work,but some easier
than others. My favorite is a parallel TT with plug in coils for 80 thru
10. It is much bigger than necessary, for QRP, but it tunes anything and I
read that it has the best harmonic rejection. My next tuner project will be
a Z-match and then a good Pi-net. I'm 74 and hope to be doing this 20 years
from now!
19. My tuner is a homebrew qrp version of the Balanced Balanced
Antenna Tuner by Measures.
Mine differs in that:
- I use seven different toroids on each antenna leg instead of
roller inductors. Their values(uh) are:
0.25 0.5 1.0 2.0 4.0 8.0 8.0 The toroids may be individually
switched in so that 128 inductance combinations can be obtained.
- I used switched capactiors. Their sizes(pf) are:
5, 10, 22, 47, 82, 160, 390. Individually switchable also
as the inductors.
- I use a current balun that is wound around a 1.4 in. diameter
type-77 ferrite core. I think its 15 turns of RG-174.
- I added a switch that allows the capacitor bank to be connected
to either the antenna side of the inductor or the rig side of
the inductor to allow matching loads above or below 50 ohms.
I have done some simple tests with it and am well pleased. It seems to
be able to match a wide range of loads over the bands I can test it on. The
balance as it is typically measured appears to be excellent. Even with
fairly unbalanced loads, a balanced current is forced into the load.
***********************************************************************
And there you have it, Gang. A lot of creativity in this group!
CUL,
Bob Kellogg, AE4IC, Greensboro, NC
Prolably, but not nececelery. - Benny Hill
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