Subject: Coax Switching

[Joseph Hurd]

Gentlemen,

Researching the adjacent seperation (?) of the coax switch "ports" themselves of various makes would be in order. I feel sure that various makes of switches offer various levels of (dB) isolation between "ports". What may work o.k. barefoot may cause damage with the amp running for a certain make and model but not another. I would try to find the manufacturers stated seperation and calculate for adequate separation first. The other option (aside from a lab test) is a smoke test..... 

Joe AF6G
_____________________________________________________
Hi Bernie

Several years ago, many of us contest types used "cascaded" Daiwa 2
position switches along with two B&W 6 position rotary switches to switch
various antennas to either of two rigs. It was rather complex to say the
least!. But it did work at 1.5KW power levels. Since then, a better solution
was developed (see the last ppg of this post)

If we assume that the A/B switch (radio selector) has 40 db of isolation (a
reasonable figure for the typical Daiwa 2 position switch), and you are only
running 100 watts, the risk of damaging the "off-line" radio should be low.

In your case, if you are using the Heathkit rotary coax switch to do the
A/B radio selection, I'm pretty sure that switch doesn't have more than 30
db of isolation between ports and its a good bet that you had a watt (or
more) into the front end of the TS830.

If you are going to do the manual switching scheme using the A/B switch (to
select either the TS830 or TS430) and the Heathkit 6 position switch (to
select the antenna), use the best 2 position switch you can find (maximum
isolation between ports).

Contact me via email at K5RT at Verizon.net. I have a couple of Daiwa 2
position switches in the drawer here. I'm sure we can make a deal. Be
patient, I'm going to be away for the week, but I will get back to you.

One idea you might look into if you have the extra scratch is the Array
Solutions "Six Pack". This is a 6 x 2 antenna switch matrix, so you can use
either radio into any of 6 antennas. It has interlocks designed in so that
its impossible for two radios to access the same antenna.


Paul K5RT



> -----Original Message-----
> From: Heathkit Owners and Collectors List
> [mailto:HEATH at LISTSERV.TEMPE.GOV]On Behalf Of Bernie Arcand
> Sent: Saturday, January 06, 2007 5:20 PM
> To: HEATH at LISTSERV.TEMPE.GOV
> Subject: Coax Switching
>
>
> Hi guys...
> I have a Heathkit Coax switch that I built decades ago, and now
> that I have two rigs, I have the output of both of these rigs
> into the switch, with the common port the output to the
> tuner/antenna.  Question:  Is there a possibility or potential or
> likelyhood that by transmitting on one radio, that I can damage
> the receive on the other radio when it is turned off?  Would I
> decrease the likelyhood of damage if I turn on the RF attenuator
> on the unused rig before I turn it off?  I realize the safest way
> is to disconnect the coax and terminate it into a 50 ohm
> load...but don't want to do that.  Simply want to switch between rigs.
>
> I don't know if I was just used to the dimished receive
> capability ion my Kenwood TS830S and didn't realize it until I
> compared it to the Kenwood TS-430S, which is super hot!
>
> Just wondering what your opinions are...any and all...but rest
> assured, I'm not trading my Kenwoods for a /\/\.
>
> Bernie in ND
> WD0GMD
Joseph Hurd, AF6G

jehurd at darrcam.com

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