[R-390] Balanced input on higher bands correction

[Jim Whartenby]

Thanks Dave,I didn't know about the balun, I wonder it covers the MF and HF bands?  I have the UG-971/U here which was what I was thinking about.
Jim

Too much agreement kills a chat.  E. Cleaver

-----Original Message-----
From: Dave Merrill <r390a.urr at gmail.com>
Cc: R-390 at mailman.qth.net <r-390 at mailman.qth.net>
Sent: Fri, Dec 24, 2021 10:07 am
Subject: Re: [R-390] Balanced input on higher bands correction

IBM used twinax on their System 34 token ring network and at least some of
the twinax to BNC adapters you'll find are from those networks. They
contain a balun which may or may not be responsive at HF frequencies.

A safer bet is a UG-971/U and a UG-636A/U C to BNC adapter. Both of these
are found in the MK-288 Maintenance Kit.

NOS UG-971/U adapters are available very reasonably here: eBay item
312574496229.

The UG-636A/U can be found on eBay for about $20.

73 & Happy Holidays,

Dave N9ZC

On Thu, Dec 23, 2021, 11:11 PM Jim Whartenby via R-390 <
r-390 at mailman.qth.net> wrote:

> Jordan There are Twinax to coaxial adaptors available so you don't really
> need to jury-rig the connection.  I believe that you have a choice of
> Twinax to N, BNC or UHF.
> There is one on eBay, Item # 401412862478 which adapts Twinax to BNC.
> Another is Item # 132072997494 which is Twinax to UHF.  If you are patient,
> the perfect adapter for you application will eventually show up, at a
> decent price.
> Not my auctions, don't know the sellers, etc.  <grin>
> Jim
>
> Too much agreement kills a chat.  E. Cleaver
>
> -----Original Message-----
> From: Jordan Arndt <Outposter30 at shaw.ca>
> To: R-390 Forum <r-390 at mailman.qth.net>
> Sent: Thu, Dec 23, 2021 12:38 pm
> Subject: [R-390] Balanced input on higher bands correction
>
>
> Hi group and Happy Holidays...
>
> Sometime back I responded to a post stating that my 390As all had an issue
> above 15-16Mhz when connected to my ~90 foot wire via the balanced antenna
> input...
>
> The problem was not the antenna or the balanced input. The real problem
> was
> that I was temporarily using an 18" jumper to ground one side of the
> balanced input connector to the chassis.
>
> Once I replaced the 18" jumper with a 2 inch wire grounded to the mounting
> screw just below the balanced input connector, the sensitivity was
> restored
> from 15 to 32 Mhz. In fact, I'm surprised at how much of a difference the
> length of that connection made...
>
> Live and learn...!
>
> 73...Jordan VE6ZT
>
> ______________________________________________________________
> R-390 mailing list
> Home: http://mailman.qth.net/mailman/listinfo/r-390
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:R-390 at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> ______________________________________________________________
> R-390 mailing list
> Home: http://mailman.qth.net/mailman/listinfo/r-390
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:R-390 at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
______________________________________________________________
R-390 mailing list
Home: http://mailman.qth.net/mailman/listinfo/r-390
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:R-390 at mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html