Long Wire - 90 degree "L" - 45 degree Dipole - 90 degree Dipole

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prcguy

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A short active whip is a E-field antenna that is very high impedance and sensitive to its surroundings. In my experience it will benefit from a large ground plane like sheets of chicken wire to help isolate it from things and interference below radiating from inside your house. They are also affected being under stuff like wire antennas or power lines overhead, under eaves, etc. Since they are vertically polarized and most man made noise propagates vertical pol, they will pick up more RFI than horizontal antennas.

To add more, I've tested several passive vertical HF whips with high ratio matching transformers in the base like the AOR SA7000 outdoors on my patio and another used by the military (https://radiorecon.com/application/files/4015/6466/4024/Flexmaster_Technical_Data_Sheet_5-28-19.pdf), my active AMRAD VLF/HF whip on the roof and my W6LVP active loop worked better than all others when it was indoors next to my computer and plasma TV. I couldn't believe it.

Yes we have one or two articles on Bonito products (and some other wide band active dipoles), along with some articles from SWLing.com here...


The more I've been reading on the subject, it seems these actives really need to be grounded - and perhaps, use a common mode choke or two - to really perform well. Loops simply don't need or use any extra grounding, although the feedline might benefit from a common mode choke if it runs near computers and other noisy house electronics.

If you really want to dig into the science of antennas - and if you want to have a somewhat more efficient antenna than just throwing up a piece of wire - it's hard to argue with the publications of the Radio Society of Great Britain, which is the sister to our ARRL. Their books are simply a great resource to have around..


Mike
 
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ka3jjz

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The W6LVP loops are very popular, and deservedly (including his outstanding customer service), but I suspect that the OP (who lives in the UK) would incur an awful lot of extra outlay because of customs, shipping, VAT, etc. Wellbrook is very much in his back yard, so those charges won't apply. They have gotten awards from the WRTH so it's not like they're an unknown factor. They've been around a long time

Mike
 

Scan125

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Do a Google search on 'par ef-swl antenna reviews' and you'll come up with a ton. I highly doubt anyone will have anything really bad to say

Vibroplex took over the PAR antenna line a year or two ago - here is the direct website


Mike
Thanks for the link.

The sloping set-up performance looks really good and pretty non directional with the lobes only approaching those of the horizontal at the 30MHz end.

Now if you read back I already have a sloping set-up and similar length. My slope is from 20ft approx (English house two story gutter height) down to 5 ft over a similar length. So not far off the suggested PAR set-up. Not sure what extra there is to gain by lowering the 5ft end? other than creating a obstruction at ground level.

The 9:1 balun (I used to use one (still have it available) I removed some time ago because when I used it with an MFJ956 I found little effect and selectivity compared to having no balun. Things were even better improved with the MFJ-959C but I have not assessed a balun and 959C combo but I strongly suspect it will be like the 956 combo and of no real advantage.

So on the face of it apart from my current lower sloped end passing through some foliage it looks like I'm in pretty good shape overall.

Thanks for every ones comments etc.

When I get a chance I'll fire up my Nano direct to the antenna and via the ATU and do some sweeps.
 

ka3jjz

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Baluns have nothing to do with selectivity - the transformer on the end of the PAR is trying to take the balanced load (the antenna) and feed as much energy down the unbalanced load (the coax). It may also help with keeping noise down if grounded. Selectivity is really a function of the receiver, not the antenna. However...

There are antennas - apart from loops - that are directive. The classic dipole is directive broadside from the antenna, for example. For a multi band approach, the Beverage is one that, while often cut for a particular frequency, is pretty widebanded, and is responsive off both ends. This does depend on how high the antenna is from the ground, frequency, surrounding objects and many other factors. Very few folks have the room for a Beverage, though (heh)

I think you will find the transmatches you have probably won't do all that much for the PAR if you put a longer wire on it. One use for a transmatch is to try to get a bit more RF from an antenna that's too short for the desired frequency. However you will hurt nothing by trying it.

You will need to play around with the transformer connections to see which one works better. There's no real guide for this. Use one set of connections, try it for a few weeks, don't like it, change it.

Mike
 
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