I have a CD rip where I hot swapped two different antennas back and forth into the NAT01. One was a properly aligned G17, the other was a 5m length of NACA5!
Both of these ‘antennas’ gave a full signal strength reading on the 01, but one sounds very much superior to the other.
If you are interested, I can send you the rip of this comparison.
This is not surprising - with a stereo FM signal strength is only one of the attributes to assess - the other is signal quality - and with stereo this becomes essential. Multipath reflections and even rear interference won’t detract from signal strength (certainly as measured by a consumer tuner which likely will incorporate AGC anyway internally) but can significantly affect signal quality.
Yagi antennas with at least one reflector and multiple directors are going to help with signal quality - as well as using a BalUn if the downfeed is coax
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Should we all have a Balun between the socket in the skirting board and the back of our NATs?
A balun is mounted at the antenna dipole/loop centre point.
With a receiving antenna as we all have on our NAT tuners, its connected with an unbalanced coax cable to a balanced dipole/loop antenna.
Most FM aerial brands don’t fit them as they work OK without them, however IMO these ‘OK’ aerials can work ‘better’ with one.
I’ve experimented a lot with balun on my attic mounted Ron Smith G-14, choke, coiled coax, sleeve & lambada. All made marginal improvements, interesting experiments, however I’ve ended up with three chunky ferrite clip-ons on the coax just before the J-box.
I don’t know what a J-box is but thank you.
Ron, there is a bit of me that would just love it if that length of NACA5 did the better job…
I fully expected the G17 to be better than the NACA…what surprised me was HOW much better it was, and how easily it was to discern the differences even after the hotswaps were converted to .wav files after being burned by a dedicated CD-recorder. The NACA (and presumably most ‘wet-string’ type T-dipoles) had a small white-noise type hisssss in the background-in spite of the signal strength LED being fully bright, that wasn’t too intrusive. However the fullness, body, dynamics and sheer realism of the reproduction was pale compared to the G17.
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Hi Chris, the Balun is designed to be built at the antenna end, and it allows the Yagi antenna, which is a balanced antenna, to couple to coax cable which is unbalanced cable efficiently whilst retaining the antenna gain pattern, and minimising interference and noise coupled in the coax shield from affecting the quality of your signal… The Balun can also be designed to impedance match to align the design of your antenna impedance with 75 ohm coax.
A Balun at the tuner end will therefore serve no purpose and simply attenuate the signal further.
The Balun is about optimising the performance of a balanced antenna design into a unbalanced down cable (coax) feeder and a tuner expecting unbalanced antenna feed (ie a coax connector). But the tuner itself doesn’t care.
There are some tuners, quite rare these days, that can also accept balanced feeder, usually at 300 ohm… and usually the connector is two screw connectors side by side… and you can attach balanced ladder line cable to the tuner… and that can connect optimally to a balanced antenna with out a Balun, but perhaps just an impedance transformer. However ladder line cable is sensitive on placement with respect to nearby metal and other wires, and so is no where near as flexible as coax which is why I guess it’s fallen out of favour these days for consumer setups.
BTW NACA5 could be theoretically used as balanced feeder… I don’t know what’s it’s impedance would be but could be fun to experiment, it could then connect to a folded dipole made with NACA5 or better still NACA5 which is pulled apart by about 75 cms each side… it could be ok as a dipole setup… all depending on its CI… and dimensions of course.
Thanks Simon for explaining. I can rest easy!
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