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Old 28th Sep 2018, 11:49 am   #1
Chris 1155
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Default Kenwood TS700G OM320

Hello,
I have a recently obtained TS700G which works OK but has a crude modification using an OM 320 amplifier module. I have yet to determine the function of this mod but would like to obtain a data sheet for the OM 320 first. I do not seem to be able to source one on the internet, can anyone help?
Thanks Chris G4BYZ
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Old 28th Sep 2018, 11:55 am   #2
ms660
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Default Re: Kenwood TS700G OM320

Was the info in the link of no help?

Lawrence.
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Old 29th Sep 2018, 3:38 pm   #3
Jon_G4MDC
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Default Re: Kenwood TS700G OM320

I found it useful Lawrence, came across some years ago but had forgotten what they were. Wondering what purpose it has been turned to in a TS700G all the same..
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Old 30th Sep 2018, 5:40 pm   #4
Chris 1155
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Default Re: Kenwood TS700G OM320

Hello Lawrence,
Sorry for the late acknowledgement but the link has given me the information I wanted, thank you.
I will post the application for the 700g when I have investigated.
I bought the 700g from an auction site as spares or repairs but it does work fine as it is. When I get round to cleaning and tidying up I will be able to investigate the application of the amplifier.
Regards
Chris G4BYZ
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Old 1st Oct 2018, 8:05 pm   #5
Chris 1155
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Default Re: Kenwood TS700G OM320

Lawrence,
Sorry I missed your reply on my first posting, I am not very experienced on the use of this site.
I have now investigated the TS700G and have discovered that the OM320 module is used as an untuned RF amplifier connected between the antenna change over relay and the input to the receiver.
I believe that that the 700G was regarded as being somewhat deaf and this mod was probably carried out to rectify this.
It seems to work OK but when I get round to the refurbishment I will try the receiver without the amplifier and compare the difference.
I do have a separate vhf amplifier for TX and RX and I will also try that.
I will not start this for some weeks but will post my findings.
Thanks again,
Chris G4BYZ
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Old 1st Oct 2018, 10:30 pm   #6
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Default Re: Kenwood TS700G OM320

Interesting Chris, I suspect it made the S meter move further up the scale but much more likely it made the RX deafer in Sig/Noise terms than it was before.
My advice would be to remove it altogether but completely up to you of course.
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Old 2nd Oct 2018, 10:55 am   #7
Chris 1155
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Default Re: Kenwood TS700G OM320

Hello Jon,
Thanks for the comments.
The S meter certainly does not return to zero but I have not attempted to adjust it yet.
I will experiment with and without the OM320 and also using a 2m TX amplifier which combines a receive amplifier as well.
I am postponing the investigations until a little later in the year when indoor activities are preferable. At least I now know about the rather poorly carried out mod and feel that I have the basis of a very niece transceiver.
I have now idea why I need all this stuff as I already have a perfectly good TS700G and also an FT221. But as we all know the radio thing can be quite addictive and is of great interest.
Regards
Chris G4BYZ
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Old 2nd Oct 2018, 1:25 pm   #8
Steve G4WCS
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Default Re: Kenwood TS700G OM320

the OM series of hybrids were designed as wideband preamps for use as TV masthead amplifers etc. totally unsuitable to place at the front end of a 2M receiver.

if it does need a preamp its better with a low noise design with a tuned bandpass input, there's a good article here

https://www.qsl.net/sv1bsx/vhfpre/vhf-pre.html
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Old 2nd Oct 2018, 2:08 pm   #9
Chris 1155
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Default Re: Kenwood TS700G OM320

Hi Steve,
Thanks for the interest and information.
I have downloaded the documents and will have a go at construction in the autumn.
Results will be posted.
Chris G4BYZ
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Old 2nd Oct 2018, 2:29 pm   #10
Steve G4WCS
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Default Re: Kenwood TS700G OM320

Hi Chris.

no worries, there's also a design here that may be more repeatable, assuming the MC108 coils can be sourced.

https://www.americanradiohistory.com...RT-1983-01.pdf

there's a possbility I MAY have a PCB negative still in a folder, I will have a look

Steve
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Old 2nd Oct 2018, 10:47 pm   #11
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Default Re: Kenwood TS700G OM320

Couldnt find a pcb negative but went one better . We ran a batch of Pcb’s off for a 3sk88 preamp years ago when my job was a paid hobby. I think this was a 6m version from looking at the tuned circuits, but can’t for the life of me think what design parameters or article we stole. (It may be in a folder in the shack t be unearthed) If you could use a pcb, pm me your address 😁
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Old 6th Oct 2018, 4:48 am   #12
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Default Re: Kenwood TS700G OM320

hi all ive one of these 700g models,its deaf as a post,the ferrites have been busted in the transformers in the nb board,anyone know where i can get replacements?,cheers m3vuv.
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