End Fed Dipole Receive issues...

[T23]

I have an end fed dipole for 40 meters, but when I use it to receive on 20, 11 and 10, I get very low received signal strength. A signal might peak at an S-3 TOPS with all the pre-amps on.

Would an antenna actually made for these other bands receive significantly better?

T23

 

[Justme]

End fed wire you mean, it has no counterpart so it is just an end fed wire.
Fed with what a 1:9 balun? mostly these contraptions don't work that well.

PD7MAA HOMEPAGE: Multiband end fed antennas 3.5 - 30mHz scroll down a little, that are the ones i build, now making one with 2 stcked T 240- 43- 61 cores good for at least 400 + watts, working like a charm, having the 40/20/10 model, now going for the 80/40/20/15/10 meter model, which used with a tuner can be used outside the band as well.

The difference with the stadard 1:9 balun and wire is remarkable better recieve and transmit.

 

[KC9Q]

I've built antennas like this one: http://www.angelfire.com/electronic2/qrp/unun.html

Just replace the T130-2 core with a more appropriate FT140-61 ferrite. You should be able to receive from 1 MHz to 108 MHz with this antenna. TX will be limited to 40 to 10 (maybe 6) Meters with a tuner.

If you have an antenna analyzer you can plot the SWR curve and get an approximate idea what the antenna's performance is for TX. As far as receiving it should work like gang-busters.

Just be aware that the bands have been poor the last couple of days due to very low solar activity. 40 Meters has had extreme QSB, and poor performance on 15 to 6 Meters (exceptions have been sporatic E openings on 10 and 6). It is possible your antenna is working just fine bar these conditions.

 

[W5LZ]

Can a non-resonant antenna be used for receiving on most other bands? Sure. Will it receive as well as a resonant antenna? No. And that's absolutely normal.
Most random length antennas are usable on more than one frequency/band, but those 'usable' bands are harmonically related and are determined by the antennas length or 'loading'. All of this is about how the thing will -work-, how it will radiate or receive, it has nothing to do with the input impedance at the frequency of use (SWR). That is handled by a 'VIMD', a Variable Impedance Matching Device, located in the appropriate place, typically the antenna's feed point. What the #3|| is a 'VIMD'? It's the same thing as a tuner. Will it improve receive? Yes, but don't expect miracles. Won't that mean there'll be losses? Sure, but not as much as not using one would mean (both transmitting and receiving).
Think about it, it's what's done on almost every 'multiband' antenna on the market...
- 'Doc

 

[T23]

This still does not explain the poor receive on the higher bands such as 20, hearing the signal reports on the traffic I hear does not add up with the results I see, most stations from 20 to 10 don't even show on the s meter with all the pre-amps on.

T23

 

[M0GVZ]

Can a non-resonant antenna be used for receiving on most other bands? Sure. Will it receive as well as a resonant antenna? No. And that's absolutely normal.

Sorry but that is incorrect if you are using a tuner. Once you start getting to the point where that wire is >1⋌ then it generates lobes that have several dBi of gain as well as nulls that can be quite down. The higher you go aboe 1⋌ the more they increase in number.

You do have feeder losses because of SWR but those can be mitigated by using a balanced feeder or more ideally an antenna coupler at the feedpoint of the antenna.

 

[M0GVZ]

This still does not explain the poor receive on the higher bands such as 20, hearing the signal reports on the traffic I hear does not add up with the results I see, most stations from 20 to 10 don't even show on the s meter with all the pre-amps on.

T23

SWR is not equal to efficiency. You could have significant co-ax losses and that would show a low SWR. If you change the length of the co-ax and the SWR changes then this will confirm you had low SWR because of co-ax losses.

Also a lot of these multiband short antennas rely on a very lossy matching section to present 50 Ohms at the feedpoint.

 

[W5LZ]

M0GVZ,
Sure it's correct, and doesn't depend on feed line length or antenna length.
I definitely agree that SWR does not equate to efficiency -except- in how efficiently power/signal is transferred to/from the antenna. It means nothing as far as the efficiency of the antenna it's self is concerned. A 50 ohm carbon resistor, or a dummy load, is a perfect example of that. Very nice SWR, but a terrible radiator.
The part that's important between a resonant and non-resonant antenna is the un-neutralized reactances present in that antenna. Reactances do not contribute to producing/ratiating power (or receiving it, same thing just different direction). That's why you want to get rid of those reactances -in- the antenna. And is the definition of resonance.
Some electrical lengths tend to produce a more 'useable' radiation pattern than others. More 'useable' because it put's a signal where you want it, or receives a signal from where you want to get it.
- 'Doc