Internal tuner with random wire

classic Classic list List threaded Threaded
2 messages Options
Reply | Threaded
Open this post in threaded view
|

Internal tuner with random wire

Bob McGraw - K4TAX
The comments are good .  But considering all the pluses and minuses, wouldn’t it make more sense to use a OCFD and not worry about ground rods, counterpoise needs, high SWR, high voltage and currents in the tuner?   A well designed OCFD with correct Balun plus a common mode choke at the feed point and another at the radio will cover 80M - 10M with much less than a 10:1 SWR.

A matched condition exists only between the ATU input and the PA output. The output voltage or current can be all over the place, including inside the ATU circuits.   And the ATU has a 10:1 matching range of 5 ohms to 500 ohms.  Random wires can easily be outside of this range.  Thus the ATU can not effectively match the load.  

Bob, K4TAX


Sent from my iPhone

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]
Reply | Threaded
Open this post in threaded view
|

Re: Internal tuner with random wire

Jim Rhodes-2
Sure if you have the time and supports, but if you are setting up a
temporary station for a few hours you don't want to waste operating time. A
9:1 or even 4:1 unun can get you on the air quick. Need only 1 support. A
counterpoise and a choke of some kind on the feedline does help.


On Sat, Dec 12, 2020, 23:22 Bob McGraw K4TAX <[hidden email]> wrote:

> The comments are good .  But considering all the pluses and minuses,
> wouldn’t it make more sense to use a OCFD and not worry about ground rods,
> counterpoise needs, high SWR, high voltage and currents in the tuner?   A
> well designed OCFD with correct Balun plus a common mode choke at the feed
> point and another at the radio will cover 80M - 10M with much less than a
> 10:1 SWR.
>
> A matched condition exists only between the ATU input and the PA output.
> The output voltage or current can be all over the place, including inside
> the ATU circuits.   And the ATU has a 10:1 matching range of 5 ohms to 500
> ohms.  Random wires can easily be outside of this range.  Thus the ATU can
> not effectively match the load.
>
> Bob, K4TAX
>
>
> Sent from my iPhone
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]