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Author Topic: Modifying various transceivers to TX in the new bands  (Read 11147 times)

KM1H

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Modifying various transceivers to TX in the new bands
« on: June 21, 2017, 05:05:25 PM »

Has anybody succeeded in opening up any of the various ham rigs TX section for the new bands? It may be as simple as clipping out a diode or two as is done to get full power 1.5-30mHz TX out of many brands and models.

All that is needed is a few milliwatts of Class A into an outboard amplifier string.

I use my TS-940 and TS-950SD all the time to RX down below the BC band and hearing things is easy with a decent antenna. Even 500' Beverages have good directivity on the LF BCB and on NDB's.

Carl
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N3QE

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RE: Modifying various transceivers to TX in the new bands
« Reply #1 on: June 22, 2017, 07:28:19 AM »

Has anybody succeeded in opening up any of the various ham rigs TX section for the new bands? It may be as simple as clipping out a diode or two as is done to get full power 1.5-30mHz TX out of many brands and models.

All that is needed is a few milliwatts of Class A into an outboard amplifier string.

I use my TS-940 and TS-950SD all the time to RX down below the BC band and hearing things is easy with a decent antenna. Even 500' Beverages have good directivity on the LF BCB and on NDB's.

I think the interstage and output transformer of a ham 160M-6M HF rig are already running out of oomph at 160M. Maybe you can get a few watts out. Everyone I know homebrews their LOWfer transmitters - most of the work goes into getting some kind of efficiency in the antenna match.

In a HF rig most of the bandpass filtering is shared with the receive section but as you point out on workable receive performance, on 160M that tends to be low-pass (maybe some rigs have a BCB reject.)
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KM1H

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RE: Modifying various transceivers to TX in the new bands
« Reply #2 on: June 22, 2017, 10:42:45 AM »

You missed my point.

Im suggesting taking the very low level signal out BEFORE it goes to any of the band/octave specific driver stages where it is then filtered, etc.

Both my Kenwoods have a transverter output of 10 mW or less which I already use to drive VHF thru microwave transverters on 10M.

Those rigs both can run full power down to 1500 kHz where a relay kicks in to stop it going any further.

They also switch in an attenuator for the rest of the BCB RX which is switched out at 500 kHz and below.
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KM1H

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RE: Modifying various transceivers to TX in the new bands
« Reply #4 on: June 24, 2017, 06:44:21 AM »

I wasnt asking about transverters.
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KD0REQ

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RE: Modifying various transceivers to TX in the new bands
« Reply #5 on: June 28, 2017, 08:05:39 AM »

I doubt you'll get anywhere with the newer computerized rigs. they already have their band limits modified for country of sale.
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KM1H

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RE: Modifying various transceivers to TX in the new bands
« Reply #6 on: June 28, 2017, 06:12:52 PM »

I dont own a computerized rig, they are both 80's era.
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WB8LZR

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RE: Modifying various transceivers to TX in the new bands
« Reply #7 on: July 01, 2017, 09:29:31 AM »

I suppose that's a thing that'll be highly dependent upon the specific rig.  I'm glad you got yours going.  I agree that there's nothing wrong with 80's rigs: my favorite HF rig is the Alda 103A (1979).  Internally, those 80's rigs were pretty hard-wired to a unique design.  The Alda starts out with a 9 MHz BFO, puts that through a 9 MHz mechanical filter, mixes that with a 5 MHz VFO, mixes that with an 11 MHz or 18 MHz oscillator, depending on band, and then puts that through the band pass and PA.  How is your rig set up?

I'm going to look at it more closely to see what would be required for a lowfer output.  Should be doable, like you said, far ahead of the filtering and the amps.  In the Alda case, there's a LPF before the 11/18 MHz oscillator, which pushes the take-off point back a little.  The prior circuits may not be wide banded enough tho ... but interesting to see ...

I think that in the future, SDR may be the way most hams will do lowfer stuff. Also, use can be made of those new synth chips (Si5351A, Si570, etc).      

« Last Edit: July 01, 2017, 09:50:17 AM by WB8LZR »
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KM1H

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RE: Modifying various transceivers to TX in the new bands
« Reply #8 on: July 01, 2017, 05:47:56 PM »

The Kenwood TS-940 and TS-950SD manuals are on the KW site.
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WB8LZR

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RE: Modifying various transceivers to TX in the new bands
« Reply #9 on: July 03, 2017, 11:37:39 AM »

The Kenwood TS-940 and TS-950SD manuals are on the KW site.

Took a quick look at the block diagram.  I think you may have an easy time with a conversion for the new bands with that 950.  It seems you already have a 455 KHz SSB signal coming out of your first transmit IF, and then the mechanical filter.  My ALDA has much higher IF.

The Kenwood has that up-converter thing going on, and in the third transmit mixer is 73 MHz - so you'll be picking the signal off much earlier than that!  Generally speaking, your old 80's rig is 3x more complicated than my old 79' Alda tho ...    :)   

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