"Rick (W-A-one-R-K-T)" wrote in message
news

I just put up an inverted V that is up about 70 feet in the center and
about 15 feet at the ends. Each leg is about 130 feet long, or about 260
feet overall, which is right around a half wave for 160 meters. It is fed
with ladder line and an LDG auto-tuner.

I also have a dipole antenna that's up about 17 feet and is a half wave
for certain MARS / CAP frequencies above the 75 meter band, hence it's a
bit short for 75 meters. That antenna is coax fed and goes through a
different LDG auto-tuner which allows me to use it on 75/80 meters with a
good match.

The long and high inverted V doesn't work any better than the short and
low dipole, and in some cases doesn't work as well.

I have checked all the connections on the inverted V and even did a
continuity check from each side of the ladder line, up through the feed
point, out each leg to the end of each leg, and all seems OK.

I have tried switching auto-tuners (taking the one that's on the coax-fed
dipole and putting it on the inverted V) with no discernible difference.

Seems very strange. Any ideas that might account for why the V doesn't
work better?


you left out many details.
1. on what band did you do these tests?
2. what where your criteria for evaluating 'better'? swr, rx noise, rx
signal strength, tx field strength, tx signal measurements by someone at
some distance from you?
3. at what distance were the stations you compared, if that is what you did?
4. at what time of day/night, and on what date (important if there was some
kind of geomagnetic disturbance or some other propagation anomaly that day).
5. over how long of a period of time have you made these observations?
6. in what directions were the stations relative to each of the v's?
7. how close together are the v's?
8. what is supporting the v's?

On Sat, 12 May 2007 13:03:31 +0000, Dave wrote:

1. on what band did you do these tests?

Mostly 80 and 40, since those are the frequencies near where my two
reference dipoles are cut (the one I mentioned, cut a bit above 80 meters,
and a second 40-meter dipole at the same elevation, 17 feet, fed from the
same coax feedline).

2. what where your criteria for evaluating 'better'? swr, rx noise, rx
signal strength, tx field strength, tx signal measurements by someone at
some distance from you?

The only criterion I have available right now is received signal strength.
I don't yet have the resources to do transmit signal strength
measurements.

3. at what distance were the stations you compared,

Some were regional, less than 200 miles away, and so of course I would
have expected the low dipole to perform well, perhaps better than the
inverted vee. However, others were 500 to 1000 miles away, in places like
Virginia and Georgia (I'm in New Hampshire). Consistently, they came in
as well, or nearly so, and sometimes better, on the dipole than on the V.

4. at what time of day/night, and on what date

I work at home, and so I am able to get on the air several times during
each day. I ran some tests on the ECARS net at 7255 during the day,
generally from about 10 AM until about 3 PM EDT, and on 80 meter CW and 75
meter SSB during the early to mid evening. I did this every day for about
the last week and a half or so (for reference, today is Saturday, May 12).

5. over how long of a period of time have you made these observations?

As noted above, about the last week and a half or so.

6. in what directions were the stations relative to each of the v's?

There is only one V, and the other is a dual band dipole (75 and 40 meters
fed with one coax). The V and the 75-meter dipole are oriented roughly
east and west, and the 40-meter dipole is oriented roughly east-southeast
and west-northwest. Most of the stations I tested with were in Ohio down
through Florida, and so were about 260 degrees true down to about 210
degrees true ... especially in the case of the Ohio stations, not really
optimal for the antenna orientation, and yet an inverted vee should have
been much less sensitive to that than a dipole.

7. how close together are the v's?

The V and the dipole are approximately 30 feet apart horizontally and 50
feet apart vertically at their feedpoints, hence their feedpoints are a
bit under 60 feet apart.

8. what is supporting the v's?

The V is supported by a tall tree in the back yard. The tree doesn't have
many branches or much foliage, and what it does have are high up, mostly
higher than the feedpoint.

The dipole is supported by trees on each end.

Rick (W-A-one-R-K-T) wrote:
. . .
The only criterion I have available right now is received signal strength.
I don't yet have the resources to do transmit signal strength
measurements.
. . .

Do you expect them to be different? Why?

Roy Lewallen, W7EL

On Sat, 12 May 2007 13:33:16 -0700, Roy Lewallen wrote:

Do you expect them to be different? Why?

Good evening Roy...

Well, yeah... sorta...

Wouldn't one normally expect a "better" antenna to be "better" on receive
(i.e. give a stronger received signal) as well as on transmit?

"Rick (W-A-one-R-K-T)" wrote in message
news
On Sat, 12 May 2007 13:33:16 -0700, Roy Lewallen wrote:

Do you expect them to be different? Why?

Good evening Roy...

Well, yeah... sorta...

Wouldn't one normally expect a "better" antenna to be "better" on receive
(i.e. give a stronger received signal) as well as on transmit?


yes, a 'better' antenna would be... but higher and longer don't necessarily
mean 'better'.

You should definitely expect the difference between two antennas to be
the same in terms of signal strength for transmitting and receiving.
However, the antenna which produces the stronger signal isn't
necessarily the better receiving antenna. What counts when receiving is
signal/noise ratio, and the the antenna producing the strongest signal
may well produce a worse signal/noise ratio.

Doing transmit signal tests is entirely useless unless you happen across
someone with a step attenuator who knows how to use it, and the patience
to make many measurements as QSB fades you in and out. A friend of mine
gets perverse pleasure out of the dramatic differences other people
report between "antenna A" and "antenna B", when they're actually the
same antenna.

Roy Lewallen, W7EL

Rick (W-A-one-R-K-T) wrote:
On Sat, 12 May 2007 13:33:16 -0700, Roy Lewallen wrote:

Do you expect them to be different? Why?

Good evening Roy...

Well, yeah... sorta...

Wouldn't one normally expect a "better" antenna to be "better" on receive
(i.e. give a stronger received signal) as well as on transmit?

I have been reading the Inverted Vee thread about the differences in
receive and s/n.

My process of using the tuner is to find the highest noise level,
then, turn on the carrier and fine tune to the lowest SWR. Often I
find that the signal strength isn't as good as it was before tuning.

Assuming the SWR is acceptable when tuned to the best signal, even
though it is not at its lowest, would it be better to leave the tuner
at the best received signal and use the radio with a bit higher SWR?

I am talking about SWR below 2:1, (not 10:1) as measured by the meter
or radio at time of tuning. For me, acceptable SWR for my solid state
rigs is 1.7:1 as 1.8:1 often causes protective circuits to kick in and
reduce power.

Comments?

Buck
N4PGW

--
73 for now
Buck, N4PGW

www.lumpuckeroo.com

"Small - broadband - efficient: pick any two."

Buck wrote:
I have been reading the Inverted Vee thread about the differences in
receive and s/n.

My process of using the tuner is to find the highest noise level,
then, turn on the carrier and fine tune to the lowest SWR. Often I
find that the signal strength isn't as good as it was before tuning.

Assuming the SWR is acceptable when tuned to the best signal, even
though it is not at its lowest, would it be better to leave the tuner
at the best received signal and use the radio with a bit higher SWR?

I am talking about SWR below 2:1, (not 10:1) as measured by the meter
or radio at time of tuning. For me, acceptable SWR for my solid state
rigs is 1.7:1 as 1.8:1 often causes protective circuits to kick in and
reduce power.

Comments?

Buck
N4PGW

It would be really neat if we had a tuner that would selectively tune
the signal and noise. But alas, we don't. At HF, the signal and noise
are both coming from outside the antenna, so anything we do at the tuner
-- or anywhere between the antenna and receiver -- affects both equally.
The tuner won't affect the received s/n ratio unless you get it so badly
mistuned that you start hearing receiver noise, which isn't likely at
HF. So tune it any way you want.

For transmitting, you're always best off getting as much power to the
antenna as you can. (I mean actual power, not "forward power".) What
you're trying to do is make the best s/n ratio at the other guy's
receiver. You can't do anything about his noise, but for every dB you
increase your signal, you get a one dB improvement in the s/n ratio at
his end. This means having an SWR low enough that your rig doesn't shut
down. Unless you have an extraordinarily lossy transmission line, any
SWR below the shutdown point will get the same amount of power to the
antenna for practical purposes.

At VHF and above, receiver noise is usually greater than atmospheric
noise, so the rules change for receiving antennas. There, you do want to
get as much signal from your antenna as you can in order to get the best
s/n ratio. The rule for transmitting is still the same, though.

Roy Lewallen, W7EL