[TowerTalk] Balun for G5RV

[DGB]

Wow, it is complicated ... no ones ever figured that out and give me an 
answer? I should have known, ask 100 hams an opinion and you'll get 200 
(at least) opinoins, non with a direct answer!

Guess I'll have to bake a few plastic boxes and find out for myself, 
once I get back up home and can run some power!

tnx all, I love it!

73 de ns9i ... dwn here in the balmi 60 deg F

On 2/1/2011 9:11 PM, Kevin Normoyle wrote:
> On 2/1/2011 6:20 PM, DGB wrote:
>> ....   and I repeat ....  is it acceptable to enclose it in a
>> non-conductive enclosure, on a multiband antenna, say resonant on 160 or
>> 80,  especially at high power (1500w)?
>>
>> 73 Dwight NS9I
> If you want to make some estimates:
>
> I used this paper before to make some rough guesses at thermal 
> dissipation for enclosed electronics
> http://www.hoffmanonline.com/stream_document.aspx?rRID=233311&pRID=162534 
> <http://www.hoffmanonline.com/stream_document.aspx?rRID=233311&pRID=162534> 
>
>
> Assume you need to dissipate 30W or so. You can derate that by some 
> duty cycle (assuming you listen sometimes? :)
> It's all about the total surface area of the box and it's material. 
> Just because it's enclosed, doesn't mean it doesn't dissipate.
> Plus: a little breeze and you've got airflow on the surface.
>
> The biggest heat rise will actually be from the sun, I believe. (see 
> evaluation of solar heat gain)
>
> Look at those charts and think about the black baluns you've seen.
> White is right!
>
> I was also going to comment on how I used 16 awg silver plated teflon 
> for my bifilar windings so I could fit enough turns but still get 
> substantial turn to turn spacing.
>
> Also, I've not seen enough agreement on the sources of stray 
> capacitance..from what I read, the winding to core substantial 
> capacitance...I wrapped my core with two layers of the yellow gas 
> teflon tape (easier to handle than the thin white stuff). I've seen 
> some stuff showing that tight winding of enamelled wire has more stray 
> capacitance than insulated wire (which gets the wire up off the core). 
> Thoughts?
>
> But then I figured I'd keep my mouth shut, because Jim will probably 
> say parallel #12 THHN has lower impedance than my #16 parallel 
> insulated. I suspect they're both about same though.
>
> -kevin
> ad6z
>
>
>