On Mon, 18 Apr 2005 12:53:26 GMT, "Dale Parfitt"
wrote:


"David" wrote in message
.. .
Make Folded Dipoles and use a CATV balun backwards at the feedpoint.
Then you can use plain old RG-6 and F-Splitters. Not only is this
incredibly cheap, the entire antenna system is at DC ground*.
Caution, do not use Baluns with little capacitor inside.

*Use an F Grounding Block where the coax enters the house. And a
drip loop.

http://members.shaw.ca/weskyscan/ima...ldedDipole.gif

There is a potential problem here in that many, many baluns and splitters
intended for CATV have very poor performance at HF- i.e. balance is poor,
insertion loss can be well above theV/U values. For the splitters, port to
port isolation can be very poor, loss higher than may be acceptable.
Finally, I have yet to see a CATV Balun that is acceptable for out door use.
I wouldn't count on the system being at DC potential either- there are
several methods for creating a 4:1 balun- and seeing as how the wire used in
these baluns is smaller than #36 gauge- it wouldn't take much to fry it
anyway.
Wouldn't it be much simpler to build a classic dipole from single conductor
wire, place several clamp on #43 cores at the dipole to feedline transition
and forget about the CATV stuff and fragile twinlead??

Dale W4OP


I have built these suckers resonant at 6 mHz and survived tropical
storms. The purpose of DC ground (easily verified with a DVM with a
buzzer) is to bleed static charges, not substitute for accepted
lightning amelioration SOP.

As far as the perfomance at lower frequencies, the little suckers work
just fine. Don't let the 5-900 mHz specs fool you. As long as there
are no serices caps inside, they work way lower than 5 mHz.

Co-ax Seal under Scotch 33+ makes anything weatherproof.

These are definitely workingman's antennas, quite modest but also very
capable. They are more wideband than their single wire equivalents
(though theoretically not usable on even harmonics.) Make 3, one for
6, one for 10, one for 15. use an A/B/C switch and you'll have a lot
of fun.

David wrote:

I have built these suckers resonant at 6 mHz and survived tropical
storms. The purpose of DC ground (easily verified with a DVM with a
buzzer) is to bleed static charges, not substitute for accepted
lightning amelioration SOP.

As far as the perfomance at lower frequencies, the little suckers work
just fine. Don't let the 5-900 mHz specs fool you. As long as there
are no serices caps inside, they work way lower than 5 mHz.

Co-ax Seal under Scotch 33+ makes anything weatherproof.

These are definitely workingman's antennas, quite modest but also very
capable. They are more wideband than their single wire equivalents
(though theoretically not usable on even harmonics.) Make 3, one for
6, one for 10, one for 15. use an A/B/C switch and you'll have a lot
of fun.

The losses are already bad at 5 MHz and get worse as you go lower.
You may get away with them, but you might not hear a really weak signal
you're looking for because of the added losses. Have you measured the
insertion losses for properly terminated two way splitters? I would
open the case, remove the directional coupler and install a couple
hybrid amps and protection circuits to help match the 50 Ohm impedance
and maybe give a dB or two of gain. Have you measured the return loss
of any of the splitters?

I built a 1 in, 32 out distribution amplifier for Microdyne to
distribute their 10 Mhz in house frequency standard. I used the LH0002
buffer amps, but there are newer parts with even better performance.
The advantage of individually buffered outputs is that any noise
generated by one load isn't reflected back into another load and you can
connect or disconnect equipment without affecting other loads.
--
Former professional electron wrangler.

Michael A. Terrell
Central Florida

In article ,
"Michael A. Terrell" wrote:

David wrote:

I have built these suckers resonant at 6 mHz and survived tropical
storms. The purpose of DC ground (easily verified with a DVM with a
buzzer) is to bleed static charges, not substitute for accepted
lightning amelioration SOP.

As far as the perfomance at lower frequencies, the little suckers work
just fine. Don't let the 5-900 mHz specs fool you. As long as there
are no serices caps inside, they work way lower than 5 mHz.

Co-ax Seal under Scotch 33+ makes anything weatherproof.

These are definitely workingman's antennas, quite modest but also very
capable. They are more wideband than their single wire equivalents
(though theoretically not usable on even harmonics.) Make 3, one for
6, one for 10, one for 15. use an A/B/C switch and you'll have a lot
of fun.

The losses are already bad at 5 MHz and get worse as you go lower.
You may get away with them, but you might not hear a really weak signal
you're looking for because of the added losses. Have you measured the
insertion losses for properly terminated two way splitters? I would
open the case, remove the directional coupler and install a couple
hybrid amps and protection circuits to help match the 50 Ohm impedance
and maybe give a dB or two of gain. Have you measured the return loss
of any of the splitters?

I built a 1 in, 32 out distribution amplifier for Microdyne to
distribute their 10 Mhz in house frequency standard. I used the LH0002
buffer amps, but there are newer parts with even better performance.
The advantage of individually buffered outputs is that any noise
generated by one load isn't reflected back into another load and you can
connect or disconnect equipment without affecting other loads.

Yes, the active devices will provide good output to output isolation.

One drawback of any passive splitter is poor isolation.

--
Telamon
Ventura, California