[TenTec] Re. [Ten Tec] Grounds and balanced fed verticals
psussman at pactor.com
Thu Jan 26 09:37:21 PST 2012
Once upon a time I used flat 300 ohm TV line and twisted it every so often.
Then I used wider spaced window line and also twisted it for a feed line.
It also worked.
Now I use homemade open wider feeder with #12 wire and 4 inch ceramic dog bone
insulators. (Yeah, once upon a time Radio Shack actually sold them.) This set-
up is very broadbanded (I use an 80m full-wave loop) and loads everywhere. I
could calculate, but my feedline loss is so minimal I don't bother.
73 de Phil - N8PS
Quoting Steve Hunt <steve at karinya.net>:
> In a typical coax line, the dielectric losses don't exceed the copper
> losses until you get above 1GHz. At HF line losses are overwhelmingly
> copper losses, and dielectric losses can safely be ignored. Do the sums
> or take a look at the chart here:
> As Jim said, the lower matched-loss of twin lead is down to its higher
> characteristic impedance (hence lower current) and, possibly, larger
> conductor diameter. Commercial window line doesn't have a particularly
> large conductor - you can make lower-loss line yourself simply by using
> thicker wire. Also, if it's open-wire line, it wont suffer anything like
> the increase in loss when wet that the commercial window line does.
> Steve G3TXQ
> On 26/01/2012 13:21, Carl Moreschi wrote:
>> Loss due to dielectric loss tangent (tan) can be very important.
>> This term is proportional to frequency, so the higher you go, the
>> more likely it will dominate overall loss (metal loss is only
>> proportional to SQRT of frequency).
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