Aerial Tuners AKA Transmatch

Tactical

What tuner are you using Watty?

watty

Needed generally for any high power linear.

Usually need below 30MHz as aerial is unlikely to be 50 Ohm at desired frequency. Aerial "tuner" is a misnomer. They don't tune an aerial at all, though the SPSC type in particular may be very sharply resonant. They purpose is to match the aerial to the transmitter 50 Ohms with as low loss as possible to avoid reflected power.

Reflected power increases heat and voltage on the final amplifier, so it may then fail.

At higher frequencies the band is a smaller percentage of the aerial bandwidth and the aerials (dipole or horn on Dish, Logperidic, slim Jim, 1/4 or 5/8th whip, yagi etc) tend to be more accurately 50Ohms across the band.

watty

I have a home brew simplified version of a KW107 "SPSC" type transmatch which has two aerial connectors, one for higher HF bands and one for lower HF bands. I have a 66ft (approx 20m) horizontal end fed wire on one (good for 80m and up) and an slanted vertical wire to pole on gable end for higher bands. Power handling depends on aerial & band. If the wire is too short for band the power is limited as the voltage gets to several thousand volts and the capacitors flash over. 200W is possible with sensible aerials on it.

I also have a T1 elecraft AutoATU, rated about 20W continuous, can be used with my portable home brew 80W power amp on SSB (as average power is low), but not on FM. I also use it direct with the FT817ND on 1.8Mhz to 52MHz up to 5W. It will tune a CB mobile whip to 40m to 6m (or a 10m/6m dual band whip). SWR high but usable with CB base 5/8th (approx 19ft) with match coil removed at 80m, fine 40m to 6m). Not enough inductance to tune even 66ft wire on 160m...

I had three other home brew units based on KW107 design, one using miniature polycons (the pocket MW radio tuners) in a very small box for 5W to 10W for FT817 or CB. One used full size parts... They are all in bits right now!

I also had a Military Racal Syncal30 100kHz to 30MHz 22W radio for a while. It uses a large internal non-metal grooved drum with gold braided wire on cord winding on /off a metal spindle to tune a 8ft whip from less than 2MHz to 30MHz. 24Volts though which is awkward. I used a 150W laptop PSU for mains and 18 x NiMh C size cells instead of original dead 19x D size NiCds (NiMH are slightly higher volts and the NiMh C about same capacity as old D size NiCd).


The FT817ND and the 80W home brew pa have built in metering that shows how good the match is. The FT817 meter is forward or reverse approximate power rather than real SWR. The P.A.'s meter has to have FWd power adjusted to full scale to allow reverse power (both are current or voltage really) to be read as SWR.

For the FT101ZD on 66ft wire I use a home brew meter for power & SWR based on just case & meters of a CB aerial match unit:

About 80W to 120W peak using a pair of 6146B valves driven by 12YB7(?), The rest is solid state.

The homebrew P.A. for my SDR (Software Defined Radio) or the FT817ND

You can see the SDR board beside it, a Softrock Ver 6.2 RXTX on 7MHz band (40M) with < 1W TX. Not quite enough power to drive the P.A.
The P.A. has manual or automatic band switching on filter board with six 6pole elliptical filters. Don't even consider an amplifier without some sort of tuning or filtering. The Aerial "tuner" or Transmatch does not usually provide any useful filtering of harmonics. It's quite heavy as it has an internal 7.2AH lead gel cell. The P.A. current in fully driven CW is slightly more than 10A! With speech on SSB the average will be under 3.5A. So talking with another person equally it should give 4hours plus operation. Receive current is maybe 4 x 700Ohm relays and a few LEDs



Here is the FT101ZD with the homebrew "aerial tuner" AKA Transmatch:

Tactical

Nice, very nice indeed

Great idea of having a battery for the amp too, ideal for use with the likes of the FT-817.

One day I hope to have the FT-817 I've heard great things about them.

Will take a closer look at the transmatch you've described. I'm right in thinking it can reasonably match a fairly wide range of loads on the antenna side?

Is the softrock for data only or can it also handle voice and you're quite right about the filtering too.

watty

The pocket size T1 from Elecraft will tune nearly anything except exactly 1/2 wave. Or much too short on 80m, 160m.

The KW107 homebrew is quite versatile, but not good for electrically short whips.
http://www.g4nsj.co.uk/pdf/kw-107.pdf

The one I have has just the aircore fixed coil/transformer for higher bands, the larger one for lower bands and the series variable capacitor and a dual gang capacitor in parallel with the aerial connection coils (hence it is an SCPC, serial capacitor + parallel capacitor design). It doesn't have all the "features".

They take a bit of practise to use. If I change the aerial I tune each band and stick on a new paper scale on the two knobs to mark the starting point for middle of each band. I scanned a school plastic protractor and printed it.

The Softrock works on any data or voice mode assuming you have the Software. I use a virtual Audio Cable program to connect the SDR software to MixW for data modes (saves a 2nd sound card and line out/in).

fatboymsport

i have a 817 handly little thing to have in the car will do allmost anything. hav'nt really got the most out of yet but will someday.


as for a tuner i have a palstar at1500dt

http://www.palstar.com/at1500dt.php



excellent tuner and years ahead of the junk from mfj and the like.

watty

That would do for an FL2100 OK!

1500W!

You might want to look at the elecraft T1 for smaller power!
http://www.elecraft.com/T1/T1.htm
[imghttp://www.elecraft.com/T1/T1_photo_b1_a.jpg[/img]

For 100W .. 200W auto ATU, an LDG is best value
Up to 125W
http://www.ldgelectronics.com/products.php?cID=1&pID=9&v=1

200W
http://www.ldgelectronics.com/products.php?cID=1&pID=3&v=1

All of 3 these can have auto band memory with FT817, 857, 896 and IC706MkIIg, though for the K1, only an FT817 is "off the shelf".

They are so fast than only if contesting/special eventing with bandhopping is the automatic band switch cable needed. For normal mortals it's not needed as the auto-tune is so fast.

"Clickity-Clickity-Clickity-Clickity-Clickity-Clickity-Clickity-Clickity-Clickity-Clickity"

fatboymsport

i use the Palstar with an acom1000 plenty of time for qrp when the sun gets a few spots.