eHam

eHam Forums => Antennas and Towers and more => Topic started by: VA3PUX on May 04, 2013, 06:51:36 AM



Title: Looking for better receive
Post by: VA3PUX on May 04, 2013, 06:51:36 AM
I currently have a hexbeam at 30 feet but feel the receive can be better. I am raising the
antenna another five to eight feet but that is the limit for the mast system I have in place.

In most QSOs with people using around the same power and comparable antennas my signal
report from them is always higher than the reverse. Of course there are differences in meters
but I think you get the drift.

One person thought the receive performance on a comparable two element yagi would be better
since the elements are not folded like on the hexbeam. Any thoughts on that explanation?

I have been looking at the two element Steppir yagi since it fits within the property line and
can be supported by the existing mast system.

All thoughts on this matter are welcome.


Title: RE: Looking for better receive
Post by: W1JKA on May 04, 2013, 08:25:03 AM
Is it the same on all your Hex bands?

Is your Hex rotatable? Not all propagation paths between two stations are in a straight line.

Do you have another receiver to A/B with?

FWIW:At times I have had to rotate my Hex (23 ft.) as much as 45* from direction of station I was working to bring up the receive level,this had no effect on my transmit signal or his ability to copy me.

No comment on Steppir yagis,there way out of my league.


Title: RE: Looking for better receive
Post by: W9YE on May 04, 2013, 08:51:36 AM
I have used a Hexbeam at 42 feet for the past three years.  The Hex replaced a 2 element SteppIR which failed during its second winter here.  I am unable to discern any meaningful difference in receive or transmit performance between the two beams.  I would expect a significant difference if you were to upgrade to a three element Yagi on a longer boom, regardless of manufacturer.  The only feature I do miss on the SteppIR is the 180 degree (long path/short path) button on the controller, but that alone is not worth the increased mechanical fragility to me. YMMV

73/DX de Gavin W9YE


Title: RE: Looking for better receive
Post by: VA3PUX on May 05, 2013, 06:13:14 AM
Thanks for the input - the hex is certainly on a rotor and I have noticed the side rotation to increase the signal.
The hex is not super directional but that is not a fault as I can tell if there is someone there without pointing
directly at them.

I should be able to squeeze another five feet out of the mast setup without affecting strength - higher the better tight 8-)


Title: RE: Looking for better receive
Post by: N6AJR on May 06, 2013, 10:46:46 AM
steppir now has a 3 element beam with folded elements on 6-20 meters with an overall length under 20 feet,  give them a call.


Title: RE: Looking for better receive
Post by: N6SBN on May 06, 2013, 08:36:29 PM
   People hear me and I cant hear them.   An expert told me to look for local interference from internet/tv/wifi/ powerlines etc etc.


Title: RE: Looking for better receive
Post by: AA4HA on May 07, 2013, 05:47:47 AM
  People hear me and I cant hear them.   An expert told me to look for local interference from internet/tv/wifi/ powerlines etc etc.

Interference should be pretty easy for you to evaluate. Tune to a quiet spot on a band (no QSO's) and look at the S meter to see what the "noise floor" is. The hiss should be apparent from the background static.

-then, disconnect your antenna. Ideally if you have a dummy load, switch that in instead of an antenna.-

Listen to the same spot on the band you were just listening to. Has the S meter measurement of the noise floor dropped appreciably? You should notice some drop in the background static sounds.
---------------------------
A significant difference in noise levels is a good indication that there are noise sources outside of your radio that are increasing the noise floor of the receiver.

Interference can do a couple of things; if you have an AGC circuit in the receiver it will cause the receiver to lower the gain of the incoming signals, making you "deaf" to weak signals, it can cause intermodulation in the receiver, it can cause "desense" (saturation).

Generally you will see a change in the SNR (signal to noise ratio) between a desired signal and the noise floor. This can make it hard to copy as the background static will be much more apparent to your ear.
---------------------------
Without actually going through these steps it is difficult to say that interference is your problem. There can be many other things that are causing you problems. It can also be that the other amateurs are not using quite the same type of discriminating ear (and honesty) that you have in reporting RST.
---------------------------
There is something known as "reciprocity" for transmitters and receivers. The path loss should be roughly the same for transmissions as well as reception. You may also have a receiver that has suffered from damage to the "front end" (static discharges blowing out the pre-amp or first RF stage transistors) or really needs to be re-calibrated. That can only be confirmed with a signal generator to see how sensitive your receiver really is.


Title: RE: Looking for better receive
Post by: W1VT on May 07, 2013, 06:31:36 AM
Tune to a clear spot on the dial and rotate the beam--you may find that there are directions where you can null out local noise to hear stations better.

Zack Lau W1VT


Title: RE: Looking for better receive
Post by: KD2CJJ on May 07, 2013, 11:58:01 AM
If its not interference, and its not a reactance issue then its your radio.   As mention reciprocity dictates that your transmit and receive to a station should be the same.  There are very few circumstance that this would not be the case for the frequencies and equipment you operate.  I will assume you have ruled out interference.  As the others have said if your noise floor is higher than the signal than you will perceive to not have ears.  I had this on 15 meters until I found my RFI issue.  I knew it was a RFI issue all along as I was always a S9 with noise on a band which it should not be.

I include a reactance issue because in theory you could be transmitting on a harmonic which transmits fine BUT affects the tuning of the antenna thus you cant receive AND your SWR will be acceptable.  I literally just dealt with this issue setting up my dads vertical Tarheel antenna as a base.  Even though the stations could hear him he could barely hear them and some times not hear them at all (Example he made a contact to Alaska he got a 59 report but he was only hear at a 51 which was barely copy-able)  If you have an antenna analyzer look at the X value which is reactance.  If its not 0 in any part of the band you expect to be receiving on then your antenna is not "efficient" and is resonant on a harmonic which would have a relatively acceptable transmit level and fool you by giving low SWR recordings BUT also have horrible receive performance.  Unfortunately the operator helping my dad out tuned the tarheal to just impedance... which 99% of the time is correct but some times there can be a second or third harmonic which can fool you into believing the antenna is resonant and efficient but in fact it is not...  He fixed it by re-tuning the antenna where reactance was close to 0 and impedance was roughly 50ohms making the antenna resistive...  Bing.... He now has ears!!!  All is good..

Lastly, the radio can affect receive performance though less than the antenna  system or interference.  BUT if your receiver is defective you would also experience this symptom. Good transmit but poor receive.  Its simple to test, just hook up another receiver and see if there is a noticeable difference.

The only thing we didn't mention  "My ....  is broken thus I need an excuse to buy a new and better one!" addiction.  We all suffer from this, so if this is the case we all give you permission to take another hit and fill that void!

I currently have a hexbeam at 30 feet but feel the receive can be better. I am raising the
antenna another five to eight feet but that is the limit for the mast system I have in place.

In most QSOs with people using around the same power and comparable antennas my signal
report from them is always higher than the reverse. Of course there are differences in meters
but I think you get the drift.

One person thought the receive performance on a comparable two element yagi would be better
since the elements are not folded like on the hexbeam. Any thoughts on that explanation?

I have been looking at the two element Steppir yagi since it fits within the property line and
can be supported by the existing mast system.

All thoughts on this matter are welcome.



Title: RE: Looking for better receive
Post by: NO9E on May 09, 2013, 11:19:43 AM
I have 2 el 6 band band quad at 40 ft and 2el 6m quad at 30ft. Both on top of my house. The noise floor of the quad at 30ft is some 10 db higher due to picking up more noise from the house.

The effect of higher elevation is usually much bigger than the effect of more elements. See
http://www.hamradiodeals.co.uk/forums/viewtopic.php?f=45&t=16602

More less, moving from 1/2 lambda to 1 lambda brings 6db, and from 1 to 2 lambda on far away contacts an extra 6 db. So moving from 30 to 40 feet on 20m could add 2 db and reduce the noise. For comparison, adding an extra element to a yagi usually provides 1 db.

Lots of optimistic reports by guys replacing a  $500 antenna by a $5000 antenna.  Unless the height is changed, the reports most likely have as much value as 20db extra by moving from a KW to 1.5 KW amplifier.

Ignacy, NO9E 



Title: RE: Looking for better receive
Post by: K0ZN on May 09, 2013, 03:23:27 PM
There are a large number of variables that would systematically be sorted through to get an accurate determination to your situation. I.e. local terrain, topography, urban density, coax, receiver alignment/condition, S-meter calibration, etc.  As pointed out earlier, as a minimum, you need another antenna at the same height (and not so close as to couple to the hex beam).
A dipole would be the best for this. Assuming everything is proper with the antenna and you have good quality coax, to me the next step would be to borrow another rig and compare or get mine checked and aligned.

73,  K0ZN