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Author Topic: Gonset GSB-101  (Read 2909 times)
N9XTF
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Posts: 227




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« on: March 02, 2005, 09:27:09 PM »

How can I interface a GSB-101 with a solid state transceiver?
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K0BG
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« Reply #1 on: March 03, 2005, 06:46:00 AM »

MFJ makes the device you're looking for. It is their model ARB-704 and sells for $50.

Alan, KØBG
www.k0bg.com
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WB2WIK
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« Reply #2 on: March 03, 2005, 08:18:58 AM »

That's not quite true.

The real problem is the GSB-101 does not have an internal T-R relay, at all!  It's set up to be placed in the "transmit" line between a transmitter and antenna, and has no way to bypass itself in the receive mode.

Very old fashioned technology, but then it's a very old amplifier.

The GSB-101 needs more than just the Ameritron amp interface which provides low-voltage keying.  It requires some modifications for use with a transceiver.

WB2WIK/6
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N9XTF
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« Reply #3 on: March 03, 2005, 12:21:01 PM »

The internal relay switches the transmit and receive relay for use with twins, but isn't this keyed with 110VAC?  You will have to forgive my ignorance but I do not know much about amps.  The Gonset manual shows the -100 bias for turning off the tubes during receive and a 110VAC line for switching the transmit / receive relay so the receiver gets cut out during transmit.  What actually keyes the amplifier then, just the rf from the transmitter?

Any suggestions for a modification for this amp?
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WB2WIK
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« Reply #4 on: March 03, 2005, 02:39:54 PM »

The GSB-101 gets its cutoff bias from an external source, and indeed keys the internal relay with 110v AC.  This is dangerous and won't work with any sort of transceiver, let alone modern solid-state ones.

The natural solution is to do what did with a sparkling new looking GSB-201 owned by local ham K6DNW, and that is to re-build the amplifier, using modern circuits to interface to the ancient ones already in the amplifier.

In that unit, I added an internal Dow-Key DK260 double-pole coaxial RF transfer relay as a new T/R "bypass" relay so the rig would work with a transceiver, rather than a separate TX and RX.  Then, I built a little 12Vdc power supply into the Gonset to power that relay, and added a buffered low-voltage key line input to the rear panel in the form of an RCA phono jack.  Now the rig will interface with any transceiver in the world, and keys with 12v at about 10 mA.

I also had to add an internal standby (cutoff) bias supply circuit, made with an isolation transformer and filtered full-wave bridge.

The whole job took about a day, and cost about $150 in parts, mostly because of the Dow Key dual-pole RF relay.  But it was well worth it, and now the amplifier works just like any modern amp.  Except it's still old and is rapidly becoming a collector's item, for those who choose to collect Gonset memorabilia.

They have a following here in southern California, because this is where Gonset started out and manufactured 99% of his equipment, first in Burbank and then later in Anaheim.

WB2WIK/6
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N9XTF
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« Reply #5 on: March 16, 2005, 10:40:50 AM »

Steve,

Could you sketch a rough schematic to do the proposed modifications?  Also, could you enclose a parts list.

What did you do about input tuning?  

Doug
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WB2WIK
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« Reply #6 on: March 16, 2005, 04:15:25 PM »

Doug, I didn't do anything about input tuning.  The GSB-101 doesn't have any, and the ones I've modified still didn't have any.  They worked fine, anyway, even with modern SS exciters -- although they'd be a bit easier to drive, and might allow better IMD performance from the exciters, if they had tuned input.

If you are really ambitious, you could probably wire in the Ameritron tuned input board into the GSB-101, but the bandswitch indexing isn't correct, so you might have to add a separate 5-position bandswitch just for the input.

I don't have the GSB-101 schematic or I'd be glad to sketch the changes.  If you can provide me with a copy of the schematic (soft copy, or hard copy via mail), I'll be happy to do this.

73

Steve WB2WIK/6
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VE3JJJ
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« Reply #7 on: May 04, 2005, 10:12:12 AM »

I have a GSB-101 and want to connect a transceiver as well. I was looking at the schematic, and it looks like a simple change to the wiring of the relay connections would work.

In the current wiring, the transmitter is always connected to the amplifier input. When the relay is keyed, the antenna is switched from the receiver input to the amplifier output. The receiver input is then grounded.

If one were to disconnect the current hardwired transmitter input and instead connect the amplifier input to the relay connection that is currently grounding the receiver, and connect the transceiver to the current receiver so-239 on the amplifier, we would then be effectively connecting the transceiver to the antenna in receive mode, and when he relay is keyed, connecting the transceiver to the amplifier input and the antenna to the amplifier output.


Kind of hard to explain without a diagram. There is still the issue of keying with 115VAC, but there are interface boxes to do that.

Am I missing something obvious here?
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VE3JJJ
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Posts: 22




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« Reply #8 on: May 22, 2005, 08:34:57 PM »

Just a quick update - I've rewired the GSB-101 as described, and it works perfectly with my transceiver. It's a very simple mod.
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KE4VDJ
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Posts: 4




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« Reply #9 on: September 22, 2006, 10:38:50 AM »

Greetings ,
Does anyone seem to know about TVI and this GSB-101.
It does not seem to have much shielding?
George
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N4ZAW
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« Reply #10 on: April 19, 2009, 02:54:45 PM »

I have one of these amps and would like to use it also.
However, from what I've gleaned online about this amp, it has no bias cutoff circuitry at all. So I translate this to mean the tubes are allways "transmitting", even in receive mode! I've built a couple solid state amps (2meter), nut I'm also an amp dummy (willing to learn) when it comes to tubes, grid current,bias and all that rot...

Does anyone know of a source of knowledge on building something that can control the bias in this amp -- iether homebrew, or commercially available?
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K1CCP
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Posts: 1




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« Reply #11 on: July 01, 2009, 09:42:38 AM »

2 questions.
Could I just run 2 antennas one for TX and one for Rx. and have the radio run a antenna relay?  This way I would not have to do any thing to the amp?
Also does anyone have a wiring diagram?
Sorry if the question sounds silly but I am not that up on Amps.
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