[600MRG] Some experimenting with toroids vs hollow coils on 630m

[Tom W8JI]

I build some plasma generator stuff from time-to-time, some below the 
500kHz.

The attached core stack with a two-turn CT primary would be perfectly 
fine at 50Vds and the transistors swinging the full voltage in push-pull 
at 25 amps. I actually used a single core like this in my IC751A and 
used a different binocular in the driver output and my 751A it is 
perfect even at 100W. It runs just like it did at HF.

It was like 10W and running hot with the stock ICOM cores. I can get 10X 
the power now. :)

I can swap it to 52 material and with a few more turns but the same 
ratio, or a deeper core window, have it work also.

61 is a too low on ui to be usable.

I sure wouldn't use a high ratio transformer like they use on HF in a 
reactive load on LF.    A short LF antenna has a ton of power factor 
that needs correction. It would be way better to use a high Q coil to 
match and correct the power factor all in one component.

73 Tom

On 2/16/2023 1:26 AM, John VE7BDQ wrote:
> Very interesting and thanks for posting.  Seems a lot of amateurs are 
> having great success using a 9:1 or 49:1 toroid to feed a random wire 
> on HF.  Or so they say,  Tempted to give it a try but I don't have 
> suitable cores in my junk box. Must be a matter of luck to get the 
> length of the random wire just right.
>  73   John / VE7BDQ
>
>
>
> On Wed, Feb 15, 2023 at 6:51 PM Neil Klagge <w0yse at msn.com> wrote:
>
>     The following is just my experience, not a scientific thesis  😉
>
>     These are the results of an experiment comparing a FT240-52 with a
>     hollow cylindrical coil on the ouput of my 630m IRF510 FET power
>     amplifier for 630m.
>
>     Transmitter output was 4.5w input to the toroid for this test, but
>     there was only 2w left on the output of the toroid, going into the
>     coax to the antenna. The KA7OEI-1 Northern Utah SDR was used
>     during midday to decode my signal with that core. The results were
>     worse by about 10 dB compared to when using the hollow PVC coil.
>     The amplifier ran very warm with the toroid even though my fans
>     were running full blast and even though the SWR was very low.
>
>     Using the same output power of the amplifier, the cylindrical coil
>     got a 10 dB stronger report from the SDR.  And, there was
>     negligible heating of the amplifier.   (I had similar results with
>     an FT240-43 core the previous week).
>
>     The #52 core is less than 45% efficient whereas the PVC coil is
>     about 83% efficient. The PVC coil wins!
>
>
>
>     Next, I experimented with the 52 core at the base of the antenna.
>     I was able to get the SWR under 2.0 at the base of the antenna by
>     adding or subtracting turns on the core. Inside the shack I could
>     adjust the SWR to about 1.2 but the amplifier still ran hot when
>     using the toroid and the reports back from the N. Utah SDR were
>     weaker by about 7 dB.
>
>     My original coil at the base of the antenna works much better than
>     the 52 core.
>
>     Hoping some will find this useful...
>
>     73
>>>     **´¨)
>>>     ¸.•´¸.•*´¨) ¸.•*¨)
>>>     (¸.•´ (¸.•`   Neil *, wØyse, DN41ah, North Ogden, Utah 84414
>
>     My ham radio website: http://w0yse.webs.com/ <http://w0yse.webs.com/>
>
>     My Faith website: http://neilsfaith.webs.com/
>     <http://neilsfaith.webs.com/>
>     ______________________________________________________________
>     600MRG mailing list
>     Home: http://mailman.qth.net/mailman/listinfo/600mrg
>     Help: http://mailman.qth.net/mmfaq.htm
>     Post: mailto:600MRG at mailman.qth.net
>
>     This list hosted by: https://www.qsl.net
>     Please help support this email list: https://www.qsl.net/donate.html
>
>
> ______________________________________________________________
> 600MRG mailing list
> Home:http://mailman.qth.net/mailman/listinfo/600mrg
> Help:http://mailman.qth.net/mmfaq.htm
> Post:mailto:600MRG at mailman.qth.net
>
> This list hosted by:https://www.qsl.net
> Please help support this email list:https://www.qsl.net/donate.html

-- 
This email has been checked for viruses by AVG antivirus software.
www.avg.com
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.qth.net/pipermail/600mrg/attachments/20230216/9b74343d/attachment.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: QRO transformer.jpg
Type: image/jpeg
Size: 391272 bytes
Desc: not available
URL: <http://mailman.qth.net/pipermail/600mrg/attachments/20230216/9b74343d/attachment.jpg>