Re: LF: No 2200m TX tonight

[Markus Vester <markusvester@aol.com>]

Hi Chris, Paul,

> I have always shorted out any unused turns on the loading coil

I would not do that at LF because the induced current in the shorted secondary can be high and will surely increase overall losses. This is an inductive heater! My understanding is that at HF, shorting low-band coil sections during high-band operation may be necessary to avoid hitting an unfortunate self-resonance, but I always felt that this is a compromise I would rather avoid.


73, Markus (DF6NM)



-----Ursprüngliche Mitteilung-----
Von: Chris Wilson <dead.fets@gmail.com>
An: N1BUG <rsgb_lf_group@blacksheep.org>
Verschickt: Sa, 24. Nov. 2018 18:40
Betreff: Re: LF: No 2200m TX Tonight


Hello N1BUG,



Paul, I have always shorted out any unused turns on the loading coil
with no issues. The matching transformer has floating unused turns
though, but I think it's similar to yours, again no problem. The TX
horizontal main loop has plastic egg insulators from a cattle fence.
They grow green algae over time, and I have had them get iffy. The
aerial wire is UK domestic mains insulated 7 strand cable. The
insulations seems pretty robust, but given a bad insulator it will arc
down the support rope. The loading coil is wound with the
same stuff.

Saturday, November 24, 2018, 2:39:40 PM, you wrote:

> Hi Jay,

> I haven't been able to attend a flea market in years. I'm sure I can
> find a Cantenna on the auction site, but it won't be for little money.

> I've been thinking about an 800W flange resistor on a big heat sink,
> but would need to find a big heatsink. Maybe a medium heat sink
> packed in ice... or sitting in snow as the case may be!

> I did look at water heater elements after you mentioned that a year
> ago, but I couldn't find any with a voltage / wattage rating that
> looked close to 50 ohms. Also, I am not sure what the resistance vs.
> temperature curve looks like on them. I'm torn. Being on a budget it
> is always tempting to try the inexpensive route. But on those
> occasions when the inexpensive solution fails to work out, one ends
> up spending more in the long run.

> If I don't find anything with the dummy load tests, I will modify
> the coil to eliminate the shorted turn and see if anything changes.
> That's an interesting task as one must lay in the snow to remove the
> coil from the housing to get at the connections. It's all part of
> the continuing adventure... ;-)

> I'm going to stay on MF one more night as the trans-Atlantic QSOs
> are fun. But I will get the small LF PA fixed up today and be ready
> to come back very soon.

> 73,
> Paul

--
Best regards,
Chris                            mailto:dead.fets@gmail.com