[R-390] Antenna question

[blw]

>> Are you saying that CAT-5 ethernet cable is better than coax?
> 
> It depends upon what you want. If you are only receiving or
> transmitting at QRP levels, using a receiver with a balanced input
> available, want to effortlessly null out any currents that are not
> induced in the antenna elements, want to use several antennas
> without having an antenna switch or relay outside and up high,
> don't want to care if lightening zorches your expensive feedline,
> and have boxes of the stuff laying around...yes, CAT 5 is better.
> 


Yep, just receiving. I'm sort of antenna poor at the moment with 2 dipoles
up. A temporary octaloop came down this spring and the permanent amplified
loop somehow never got built before summer hit in full force. I need that
for the RBL-5. I tried both balanced and unbalanced in the past. I stick
with balanced antennas.



>> I wonder why coiling CAT-5 will slow things down so much.
> 
> Because "coiling" can allow induced peaks and nulls to develop
> in the line. Remember, those signals have very high bandwidth
> so many resonances can develop along with imbalances. If you
> had instead simply stuffed the cable into a milk jug in a random
> fashion you would not have had a problem. I've run into this
> problem all the time with network installers who are too tidy
> and like to leave extra cable coiled up in the ceiling. I just undo
> the tie-wraps and scramble it into a nice ugly ball.
> 


I didn't think about it being twisted wire. I did know it was low impedance.
I needed that extra bit for a connector later anyway.



>> I would have to feed 2 dipoles. I guess the extra twisted pairs
>> would be good for additional antennas this fall.
> 
> Yup. And you can just make a plexi disk with eight posts around
> and wire up your four dipoles in a radial or fan array.
> 
>> Okay, here is another problem. ...The new TV in the den is
>> causing light RFI every 15 kc up and down the bands.
>> The TV is 3 rooms away!!!
> 
> The question is how close it is to the antenna. Your receiver may
> be doing it's job and the TV is simply a piece of shit. I would
> first stick a wire in the unbalanced connector and see if I could
> get that TV marker generator directly, and, if so, work on cleaning
> up the TV. How do you do that (I hear you cry)? First make sure
> the HV anode connection (in the piece of shit) is good and there isn't
> a leak somewhere, next put an RFI filter on the power cord of the
> TV, and finally, trade it in for a couple of good books. The kids need
> to read more anyway.
> 
> Otto Von Helseng


I agree about books being better than vegetating in front of the
TV....unless it's news. I'm going to cover the TV some tonight with a large,
heavy cookie sheet and see what top shielding does. My coax feed slopes away
from the TV, but I went out and looked this morning I saw that both dipole
centers were just about right over that cheap TV. Rotating the TV table
didn't help any last night, so I'm thinking a heavy metal sheet on top may
help. If not, I have some thin zinc sheets that I can bend until I find a
good shield shape. Dropping the TV and saying, "oops" would sure be a lot
easier and more satisfying. I'll do the wire in the unbalanced connector
first.

Thanks for the tips.



Barry