Pages: 1 2 [3] 4 5   Go Down

Author Topic: 2 meter bent dipole versus vertical  (Read 647 times)

W9IQ

  • Member
  • Posts: 8866
Re: 2 meter bent dipole versus vertical
« Reply #30 on: June 03, 2022, 04:05:15 AM »

Regarding the power level for S9 on 2 meters, the correct level is -93 dBm, not -73 dBm. The levels for the s-meter recommendation change for the VHF and higher bands.

Not that it will matter much as I doubt there is a properly calibrated 2 meter s-meter to be found.

- Glenn W9IQ
Logged
- Glenn W9IQ

God runs electromagnetics on Monday, Wednesday and Friday by the wave theory and the devil runs it on Tuesday, Thursday and Saturday by the Quantum theory.

KK4GMU

  • Member
  • Posts: 366
Re: 2 meter bent dipole versus vertical
« Reply #31 on: June 03, 2022, 07:30:45 AM »


What does the S-meter read when there is no signal
from the repeater?

It also could be due to multipath:  in that case, the
S-meter reading often changes with modulation.  In
that case, moving the antenna a foot or two may
make a difference.  (It is different between TX and RX
because they are on different frequencies.)

My S meter reads S9 at 145.330 Mhz, the repeater frequency.  The lowest reading across the whole 2 meter band (144 to 148) is S9.  So the transmit and receive frequency difference wouldn't explain why only "receive" seems to be very noisey, and the "transmit" much clener.

On the 70 cm band, the S reading averages around 2, ranging from 1 up to 3.

In the lowered position, the tip of my antenna is around 13-14' high.  When I raise it up another 6' or so, the S reading on 2 meters stays the same. So unless the multipath distortion signal is totally vertical, could I rule that out?  I guess perhaps the noise level could change every foot or two, and I just happened to get the same noise 6' higher.

The noise/static is continuous, not pulsed in any way.
Logged
IC-7100, RSPdx, AT-D878UVII-Plus HT, TGIF Spot

W1VT

  • Member
  • Posts: 6071
Re: 2 meter bent dipole versus vertical
« Reply #32 on: June 03, 2022, 08:14:33 AM »

Transmit is good and reception is bad because the noise is at your antenna. Mostly likely within a few minutes walking distance.  The repeater 12 miles away is unlikely to hear the local noise source that is disturbing your reception.

An Easy to Build Rear Mount 2 Meter Yagi
QST June 2012, pp 39-40
Beam your 2M signal toward the direction you want to work.
http://www.arrl.org/files/file/protected/Group/Members/Technology/tis/info/pdf/yagi.pdf
Download available to logged in members.
« Last Edit: June 03, 2022, 08:19:35 AM by W1VT »
Logged

WB6BYU

  • Member
  • Posts: 20896
    • Practical Antennas
Re: 2 meter bent dipole versus vertical
« Reply #33 on: June 03, 2022, 08:14:42 AM »

If your noise level is S9 across the band, then you
have a local noise problem that is garbling the
received signal. 

There may be other issues as well, but you need to
fix that one first.

A common approach is to power your radio from a
battery and shut off power to the house.  If the noise goes
away and the S-meter reading drops with no signal,
then the noise source is probably something that you
have control over.  Then start switching on one circuit
at a time in your house to narrow it down.  At that point,
you might have to unplug (not just turn off) each item
on that circuit to find the culprit.

That’s not perfect, though, as some devices have a battery
backup.  I have to disconnect the battery in my internet
box to eliminate the noise from it.  Pay particular attention
to electronic devices in the shack - like the desk lamp that
I had to unplug to operate.  (I’ve since replaced it with a
quieter one.)

If your transmit signal is good into the repeater, then your
current antenna is probably adequate.

W9IQ

  • Member
  • Posts: 8866
Re: 2 meter bent dipole versus vertical
« Reply #34 on: June 03, 2022, 08:22:30 AM »

Lot's of good advice on this thread.

I would recommend disconnecting your coax cable from the back of the radio and see if the S9 level drops to near S0.

What radio are you using? Some radios have an RF gain control that when reduced (generally CCW rotation), the s-meter reading will increase to show you that you have reduced the RF receive sensitivity.

- Glenn W9IQ
Logged
- Glenn W9IQ

God runs electromagnetics on Monday, Wednesday and Friday by the wave theory and the devil runs it on Tuesday, Thursday and Saturday by the Quantum theory.

W9IQ

  • Member
  • Posts: 8866
Re: 2 meter bent dipole versus vertical
« Reply #35 on: June 03, 2022, 08:52:46 AM »

Or even lots of good advice...

- Glenn W9IQ
Logged
- Glenn W9IQ

God runs electromagnetics on Monday, Wednesday and Friday by the wave theory and the devil runs it on Tuesday, Thursday and Saturday by the Quantum theory.

KK4GMU

  • Member
  • Posts: 366
Re: 2 meter bent dipole versus vertical
« Reply #36 on: June 03, 2022, 09:32:25 AM »

If your noise level is S9 across the band, then you
have a local noise problem that is garbling the
received signal. 

There may be other issues as well, but you need to
fix that one first.

A common approach is to power your radio from a
battery and shut off power to the house.  If the noise goes
away and the S-meter reading drops with no signal,
then the noise source is probably something that you
have control over.  Then start switching on one circuit
at a time in your house to narrow it down.  At that point,
you might have to unplug (not just turn off) each item
on that circuit to find the culprit.

That’s not perfect, though, as some devices have a battery
backup.  I have to disconnect the battery in my internet
box to eliminate the noise from it.  Pay particular attention
to electronic devices in the shack - like the desk lamp that
I had to unplug to operate.  (I’ve since replaced it with a
quieter one.)

If your transmit signal is good into the repeater, then your
current antenna is probably adequate.

The good news:  My antenna is probably decent.  The bad news: It's really good at picking up noise on 2 meters.

Here is the sequence of what I've tried:

1)  Unplugged both the router and modem (separate units, neither is battery powered)  No change.
2)  Plugged my power supply into my Delta lithium battery pack.  No change.
3)  While my power supply was plugged into the Delta, I switched off the power to the entire house.  No change.

What I will try next:

1) Hooking up a different 12 volt power supply to the radio.
2)  ????????????????????????
Logged
IC-7100, RSPdx, AT-D878UVII-Plus HT, TGIF Spot

KA4WJA

  • Posts: 1601
    • HomeURL
Re: 2 meter bent dipole versus vertical
« Reply #37 on: June 03, 2022, 09:39:02 AM »

Edit:  I just now saw these other two pages of posts here....oppss
I will try to read 'em and reply later.
But, what I posted here / now is good for your antenna questions!  Please read it (and heed it).


Gerry,
1)  We missed you on the tech / Q&A net last night.  And, this is a perfect question to bring up on-the-air, as many new hams would have similar queries.  (btw, we will have another tech/q&a net next Thr evening)

{of course, my usual worries here about hams looking at Amazon to find ham gear / antennas / etc., and buying "CB-brand" equipment, etc....as well as reading specs and reviews on Amazon, and trying to figure out what's what...but, I will forget these concerns for the moment}

FYI, 95% of all VHF/UHF ham communications in our county (Marion county) is 2 meters (including emcomm).....so if you feel you just "must" have 440mhz/70cm coverage, then a multiband antenna (with some compromises) might just need to be accepted by you...OR....or you could maximize your 2 meter coverage and accept limited 440mhz/70cm coverage?  (or look for different antennas...hence the purpose of this query, yes?)


2)  For VHF or UHF FM comms (as well as D-Star, DMR, FUSION, etc), you need to use vertical polarization.....not because "FM" only works vertically (that would defy Physics, hi hi).....nope....

It is because all VHF and UHF repeaters, and 99% of all VHF and UHF mobile operations are vertically polarized....so, 99% of all home station VHF and UHF antennas (for FM, D-Star, DMR, Fusion, etc.) are vertically polarized...etc. etc....so, if you wish to use FM (or D-Star, etc.), then you need to use a vertically polarized antenna!

Further fyi, if you were to use a horizontally-polarized antenna, for your FM or D-Star comms, you would be at a 20 - 30db disadvantage.....(in the real-world, I've measured "cross-pol" isolation as high as 35dB at microwave freqs, and 26 - 30dB at VHF/UHF in direct-wave - line-of-sight comms, but in general, depending on distances and antennas, figure about 20 - 26dB of disadvantage if you have the wrong antenna polarization)....in theory, this means if you have a 50 watt radio, and opposite polarization (I won't use the term orthogonal, 'cuz it will just confuse most here) you'd need to increase that power to 5000 - 20,000 watts to accomplish the same communications, you could maintain with just 50 watts and a vertically polarized antenna!   So...

So, for now.....just forget the "horizontal" antenna.  :)   (we can deal with VHF/UHF SSB and C@W comms, later)


3)  You realize that height trumps all for VHF/UHF terrestrial coverage....but, of course, you are restricted by HOA, etc....so...

So, if you wish to have better coverage "into town" / "towards town", a simple solution is a small (and stealthy) 3 or 4 element yagi....a 3 or 4 element yagi, vertically-polarized, mounted ~ 15' high, should give you good coverage into town / into the higher populated areas of the county.

Before you go any further, though, please understand that the gain figures for "the Tram" antenna are "Amazon" / "CB radio" type gain figures....'cuz it is highly unlikely that a 43" long antenna can give you 3.5dB gain over a dipole (3.5dBd)....as a 2-meter 1/2-wave dipole is 38" - 39" long....and, I suspect that "the Tram" is being "sold" as / attempted to be operated as a "5/8-wave vertical", at best...but, in reality is probably a half-wave vertical, with 0dB gain versus a dipole, at best, and more likely -1dBd!!  :(

And fyi, even in a perfect world, with proper feed and feedline decoupling, counterpoise, etc., the very best that an elevated 5/8-wave vertical antenna could manage is ~ 1.5 - 1.7dB gain over a 1/2-wave vertical dipole.....and in real-world, at best it's about 1dB better (unlikely to ever make a difference!).....but, in many/most situations, it is almost unlikely to exhibit any measurable gain versus a 1/2-wave vertical dipole.

This translates to:  Those antenna gains that you posted are total marketing BS!  Do NOT believe them! 

So, having read this....I think you now may start to see the "issue" with buying stuff from Amazon and/or buying "CB-radio-market" stuff.   (the fortunate fact is, you DO have experienced hams, right there in town that can help you, and point you in the right direction....all you need to do is ask...:)


4)   You could build a small yagi, or a simple 3 or 4 element quad (which can be pretty easy to feed directly, from one side, with coax running down a spreader and boom)....there are many on-line plans, as well as some hams local to you that have done just that!  :)   (I talked to one of them, just this week)


5)  Or you could buy a commercially made 3 or 4 element 2-meter yagi, which should exhibit approx 5 to 6dB of gain versus a 1/2-wave dipole (and perhaps even a bit more gain versus your existing "Tram antenna"?)  The azimuthal beamwidth of a small, 3 element, vertical yagi will be quite broad, and should illuminate much a quadrant....meaning if you point it roughly northeast, it will work from north, all the way to east....which is great for your locale! (notice that I'm not trying to hem you in here with exact numbers, 'cuz you've gotten then already....what I am doing is showing what should/will work well for you from On-Top-of-the-World into town)

Going any larger in size, please know that you would need to double the length of the 3 or 4 element yagi (perhaps even going 2.3 to 2.5 times its size) with a corresponding doubling of number of elements, just to get an addition 3dB of gain....and, in addition to it no longer looking too stealthy, you'd probably need some sort-of rotor to turn/point the antenna to various directions, depending on what stations/repeaters you wish to communicate with....so, as you see, since you're limited to stealthy antennas at a fairly low height, a simple 3 or 4 element vertically polarized yagi is probably the best choice for you...

If you wish to buy a new, commercially-made, 2-meter yagi....figure on spending about $100 ($75 to $120).....if you wish a used one, you can find 'em for ~ $25 - $50...

Cushcraft, Hy-Gain, KLM / M-squared, etc....have what you are looking for....even MFJ sells something that will work (on, and btw....Cushcraft and Hy-Gain are both owned/operated by MFJ now-a-days....so, quality is a crap-shoot....which is why I'd actually recommend you buy a really old, used, Cushcraft or Hy-Gain 2-meter yagi!)


6)  Oh, boy....there is a lot more to all of this, but I just now saw that there are two more pages of postings to your query here....and, I need to read them! (oppss)

And, of course, I'm hesitant to actually recommend a specific antenna, from a specific company, since as we already know from past experience I will not recommend what you are comfortable with....(hint, look at HRO, DX Engineering, Antenna Farm....for small 2-meter yagi's from Cushcraft, Hy-Gain, etc.....don't look at Amazon, nor brands like Tram, etc.)


I do hope this helps.

73,
John,  KA4WJA
« Last Edit: June 03, 2022, 09:42:02 AM by KA4WJA »
Logged

KA4WJA

  • Posts: 1601
    • HomeURL
Re: 2 meter bent dipole versus vertical
« Reply #38 on: June 03, 2022, 09:50:12 AM »

Gerry,
As I just wrote a couple minutes ago, I just now saw these other two pages of postings....
So, I just now saw this:
The odd thing is, my present Tram vertical gets good transmit comments, but reception is heavy static.

Why would transmission be good and reception be crap in the same contact?  I triple checked the transmit/receive frequencies/offset.  Strange, yes?
Wow! 

From just this one sentence, I'm guessing that you've got some serious RFI to deal with...
I REALLY wish you had joined in the tech net last night, we could've gotten a lot sorted out...

I will read more, and offer my help (again).
More later.

73,
John,  KA4WJA

P.S.  If you have a Keruig coffee maker unplug it now....and check your noise level!
I found out about this the hard way....I bought one for my Mom and ended-up returning it (see my thread in the RFI forum here, for all the details!)
« Last Edit: June 03, 2022, 09:52:29 AM by KA4WJA »
Logged

KK4GMU

  • Member
  • Posts: 366
Re: 2 meter bent dipole versus vertical
« Reply #39 on: June 03, 2022, 10:07:48 AM »


P.S.  If you have a Keruig coffee maker unplug it now....and check your noise level!
I found out about this the hard way....I bought one for my Mom and ended-up returning it (see my thread in the RFI forum here, for all the details!)

Thanks, John.

As noted in a couple posts above, I turned off the master breaker in the house while the power supply for the radio was plugged into a battery.  Same high S9 reading - no difference.

Dwellings are belly to belly, noise could be coming from an adjacent neighbor.

But my next "easy" test is to try a different power supply.  Right now I'm using a Jetstream.  I'll report after test.
Logged
IC-7100, RSPdx, AT-D878UVII-Plus HT, TGIF Spot

KA4WJA

  • Posts: 1601
    • HomeURL
Re: 2 meter bent dipole versus vertical
« Reply #40 on: June 03, 2022, 10:36:10 AM »

Please have a look here:
https://www.eham.net/community/smf/index.php/topic,136393.msg1263844.html#msg1263844
For a wonderful / funny story of a new Keurig coffee maker!


Gerry,
Going on what you write here:

My S meter reads S9 at 145.330 Mhz, the repeater frequency.  The lowest reading across the whole 2 meter band (144 to 148) is S9.  So the transmit and receive frequency difference wouldn't explain why only "receive" seems to be very noisey, and the "transmit" much clener.

On the 70 cm band, the S reading averages around 2, ranging from 1 up to 3.

In the lowered position, the tip of my antenna is around 13-14' high.  When I raise it up another 6' or so, the S reading on 2 meters stays the same. So unless the multipath distortion signal is totally vertical, could I rule that out?  I guess perhaps the noise level could change every foot or two, and I just happened to get the same noise 6' higher.

The noise/static is continuous, not pulsed in any way.

1)  Going on what you write here, my first thought is:

a) a switch-mode power-supply (SMPS) very close to you / close to your antenna and/or close to your radio, is what is causing this noise (RFI = Radio-Frequency-Interference).

Heck, it could even be the power supply running your radio!  :(
Or, it could be a cell-phone charger, a coffee maker, etc. etc. etc...
I know that you pulled the main breaker, but did you remove batteries from all the stuff in your house that has batteries?

It would be much easier to trouble-shoot and discuss this over the phone....and, if needed one of us could stop by and help!

So, please get in touch....and we'll get you sorted out.  :)


b)  My second thought was a UPS or battery-back-up, power-supply, for an internet modem/router, cableTV box, digital telephone system...(I have also personally had this issue...solved with a few Mix 31 torroids....but, for VHF, you'd want a different mix)


c)  Since it appears that the noise is constant, not on/off at sunset-sunrise, not at certain hours of the day....it is likely something in your house, on your patio, in your attic, (or any of these locales at a close neighbor's house) that is powered-up all-the-time...(note, that while it may be switched off, it may still be radiating lots of RFI, as long as it is plugged-in....a recent example in my own life was my Mom's new Keurig coffee maker!)


BTW, some "modern" LED lighting power supplies have some wicked bad RFI on VHF frequencies!!!  (the US Coast Guard has issued warnings about them interfering with maritime comms!)
So, this is a distinct possibility....could be a neighbor's new aquarium lights, etc....could be darn near anything these days!

So, it could be just about anything / everything in your house (or close neighbor's house)....


2)  So, the best approach is (I see that you did some of this....but you wrote that you connected the battery to your power supply? assume you meant to the radio?  the power supply should be unplugged from the wall and unplugged/disconnected from the radio)

BTW, it would help a lot, if you reminded us what radio you have?

---- disconnect your radio from its power supply and unplug that power supply completely....then connect a small 12vdc battery (it can be a small battery, as all you need it to do is power the radio on receive for a few minutes) to your radio, and then turn it on....if the noise went away (or got a LOT lower), then you know it's the radio's power supply....if you have no change in noise, proceed to next step.

---- look closely at ANYTHING and EVERYTHING in your house that has any battery backup, anything that batteries in it, anything like a UPS, etc.....and remove the batteries....(this is a VERY important step that most hams unfortunately do not do....please do it, and then do as before, pull the main breaker....oh, also if you can move your car / cars down the block a couple hundred feet when you do this test....I once had a friend, whose car alarm system was generating HF RFI so bad he couldn't hear squat!) THEN

---- then, go out to your house's main breaker panel and switch off your main breaker, so that everything in your house is now completely "un-powered", except for your radio that is still powered by that small battery....if noise is still there (I hope not!), then the noise is from OUTSIDE your house and we're going to need to go further (and farther) to find it!   If the noise is gone, then you know the noise is coming from something IN YOUR HOUSE....and it will easy to find it and remove it from your house.



If you still have the noise, and cannot figure out where it's coming from...
Disconnect your coax at the back of the radio....and insert a sort ~ 19" long piece of wire (copper wire, wire coat-hanger that you stripped-off the paint/coating, etc....anything will do)....and see if the noise has disappeared or gotten lower?
If so (almost assuredly so), then you can move your radio around the house, patio, car, etc....to see where this noise might be coming from.

Again, this is way way easier to explain on-the-air, etc....so, this is the best I can do here on-line, if you desire more, please get in touch.  :)
 

And, that's pretty much the best approach to take....find the offending device and trash-can it!   (we can talk all day about ferrites, etc....but, do yourself a favor and read my recent experience with that bloody Keurig!)


I hope this helps?

73,
John,  KA4WJA
« Last Edit: June 03, 2022, 10:38:46 AM by KA4WJA »
Logged

WA3SKN

  • Member
  • Posts: 8126
Re: 2 meter bent dipole versus vertical
« Reply #41 on: June 03, 2022, 11:14:01 AM »

OK, 12 miles and 50 watts over flat terrain... the Tram should work OK for you.  You have a local noise source that is causing your problems.  You should NOT have S9 noise receiving. Period!
Locating the source can be a challenge, fixing it more so.
Are you up to building a small antenna that can be used to DF the source?

-Mike.
Logged

KK4GMU

  • Member
  • Posts: 366
Re: 2 meter bent dipole versus vertical
« Reply #42 on: June 04, 2022, 06:58:42 PM »

You should NOT have S9 noise receiving. Period!
Locating the source can be a challenge, fixing it more so.
Are you up to building a small antenna that can be used to DF the source?

-Mike.

Now that I've:

1) Hooked the radio to a stand alone lead acid 12 volt battery
2) While the main circuit breaker to the house of switched off
3) And while the UPS to my computer was switched off
4) And unplugged the power and cable to my router and modem

...and the S9 reading didn't budge on the 7100, I am ready for the next step...
Logged
IC-7100, RSPdx, AT-D878UVII-Plus HT, TGIF Spot

WB6BYU

  • Member
  • Posts: 20896
    • Practical Antennas
Re: 2 meter bent dipole versus vertical
« Reply #43 on: June 04, 2022, 10:23:10 PM »

Quote from: KK4GMU

Now that I've:

1) Hooked the radio to a stand alone lead acid 12 volt battery
2) While the main circuit breaker to the house of switched off
3) And while the UPS to my computer was switched off
4) And unplugged the power and cable to my router and modem

...and the S9 reading didn't budge on the 7100, I am ready for the next step...


That’s a good start.

The next step would be to put a directional antenna
on your radio and see if you can determine what direction
the noise is coming from.  If you don’t have one, you
may be able to borrow one from a local ham, or have
someone help you build one.

Another approach is to walk around your property with
an HT tuned to the repeater and see where the signal
is stronger or weaker.  You could do that with a mobile
rig and a battery (perhaps in a wagon) if you don’t have
an HT.

If the local club holds transmitter hunts, someone may
have suitable equipment available.

If you find a corner of the yard where the noise is weaker
then moving your antenna might solve the problem.  Or,
if the noise is coming from one direction, an antenna with
a null in that direction may work.

W9IQ

  • Member
  • Posts: 8866
Re: 2 meter bent dipole versus vertical
« Reply #44 on: June 05, 2022, 03:20:26 AM »

Have you disconnected the antenna from the back of the radio to see what effect it has on the s-meter?

Have you checked the RF gain control on the upper left of the radio - the knob that is concentric with the volume control?

- Glenn W9IQ
Logged
- Glenn W9IQ

God runs electromagnetics on Monday, Wednesday and Friday by the wave theory and the devil runs it on Tuesday, Thursday and Saturday by the Quantum theory.
Pages: 1 2 [3] 4 5   Go Up