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Author Topic: Modify AH4  (Read 1689 times)
N8BOA
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Posts: 90




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« on: February 14, 2013, 10:26:19 AM »

Modify AH4
Has any one ever tried the following
1) Use the small coil and cap relays in the AH4 to drive "real relays" that can handle some power ( i.e.throw the old into the scrap pile)
2) replace the toy caps and coils with equivalent "real Coils and caps" that can handle some 'Real" power 1Kw

My concern is that the bigger relays will not be able to keep up physically and I don't think you can re-program the firmware to slow the tinning process down
The perpose is simple build a "real" automatic remote antenna tuner that one could hook up a real radio to and not worry about bad behavior
Well??

N8BOA
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N8BOA
Member

Posts: 90




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« Reply #1 on: February 14, 2013, 10:29:13 AM »

More
  Of course the "Real" Parts would have to live in a bigger box OF Course
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W9GB
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Posts: 2623




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« Reply #2 on: February 14, 2013, 10:31:58 AM »

Why bother modifying the Icom AH-4, which is a cross-market product -- originally developed for Icom's Marine markets.

Palstar, Alpha and others are offering (or completing development)
on legal limit HF automatic tuners.
http://www.palstar.com/
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N8BOA
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Posts: 90




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« Reply #3 on: February 14, 2013, 10:47:45 AM »

"Why bother modifying the Icom AH-4, which is a cross-market product -- "
Palstar, Alpha and others are offering (or completing development)
on legal limit HF automatic tuners.

They are not remote tuners my antennas live 300 feet from the house  trust me I have looked at them and wished they would have a Enet card so I could put one in a hut
MFJ has started making one but read the reviews
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N3JBH
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Posts: 2358




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« Reply #4 on: February 14, 2013, 01:38:26 PM »

I don't know the reviews on the MFJ auto tuner's look spot on for me considering there MFJ.  Grin   M artins Fine Junk.
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W9GB
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Posts: 2623




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« Reply #5 on: February 14, 2013, 03:56:28 PM »

Quote
They are not remote tuners my antennas live 300 feet from the house
Pat -

Understood.  My long-time Elmer (and retired broadcaster) has same need.
It's too bad that MFJ, Palstar and Alpha are really "tone-deaf" about the issue ...
Collins, military mfg. and commercial broadcasters have produced various solutions over past decades.

Maybe Array Solutions should build one.
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WB6BYU
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Posts: 13243




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« Reply #6 on: February 14, 2013, 04:27:39 PM »

Unless you are continuously changing your antennas, they should always match on
the same setting for each band.  So rather than having to match a wide range
of impedances, the tuner just has to match one impedance on each band.  (Well,
perhaps a few impedances to cover 160m, 80m and/or 10m because they are
wide bands.)

So if you have "real" relays and "real" coils and capacitors, find what combination
you need to match on each band and attach them accordingly to the relays. 
This was a fairly common approach before the advent of autotuners for the masses,
typically using a multi-conductor control cable to select a set of coil taps and
fixed capacitors for each frequency.  At best you just need two relay poles per
band for the input and output of the matching network.

There are other methods as well:  for example, if you arrange a set of relays to
choose a binary sequence of coils or capacitors, you can drive it with an ADC
output, then use a pot in the shack to generate a varying DC level, such that
the resulting inductance varies with the voltage.  With three such controls you
can remote your tuner.  Then you can also make a bank of switched trimpots
for each band, in effect a manually adjusted analog memory.  (Or just mark the
controls for each band with yellow sticky notes as I do with my conventional
tuners.)

If you want to use analog adjustments rather than the relay-switched steps,
you can link a pot to the shaft and build a servo so that a capacitor rotates
until the voltage from it's shaft indicator matches that from your reference pot,
again providing remote control of the tuner elements.  (A bit more difficult with
a roller inductor, but still possible.)

All of these would permit the remote control of a tuner and would be adaptable
for whatever voltage / current levels your relays could handle.
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AA4PB
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Posts: 12840




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« Reply #7 on: February 14, 2013, 04:33:18 PM »

The MFJ-998 is a 1.5KW remote tuner.

Also remember if you do your own, that the currents and voltages present (thus the ratings of the coils, capacitors, and relays) depend on the impedance you are trying to match in addition to the applied power.
« Last Edit: February 14, 2013, 04:37:11 PM by AA4PB » Logged
W9WQA
Member

Posts: 134




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« Reply #8 on: March 09, 2014, 09:58:14 PM »

a lot of work!.i dont think the speed would matter. it keeps trying till it gets results right?
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