On Monday, October 15, 2012 2:59:37 PM UTC-5, Boomer wrote:
(A G5RV) is not actually a bad antenna on 20 meters. However, the
performance on 75 is abysmal.

Would you please itemize the losses and radiation patterns that explain why you believe that to be true for 75m?
--
73, Cecil, w5dxp.com

On 10/15/2012 6:42 PM, W5DXP wrote:
On Monday, October 15, 2012 2:59:37 PM UTC-5, Boomer wrote:
(A G5RV) is not actually a bad antenna on 20 meters. However, the
performance on 75 is abysmal.

Would you please itemize the losses and radiation patterns that explain why you believe that to be true for 75m?
--
73, Cecil, w5dxp.com

I don't have any of the math for you. However, I know what works and
what does not. You probably do not listen to your own G5RV. Its poor
performance is pretty clear to anyone who listens to you. However, if
you have an emotional bond with your G5RV, I would not want to be the
cause of any alienation in your relationship. Keep using it. The low
effective radiation makes for more band space for the rest of us. The
signal just disappears into the noise level.

Better yet just put up a random wire and a water pipe for ground. You
can get a perfect match with a tuner. It will work better than the long
wire the guy wanted to bury in the ground :-) In fact I recommend you
try burying your G5RV and make a stealth G5RV. It will still load with a
good tuner.

However, if you were actually interested in improving your transmitted
and received signal, you might tune around 75 and listen to those
stations putting out a big signal. Especially in the daytime when band
conditions are bad. Ask someone with that big signal what antenna they
are using. If they are using a G5RV then you are right and I am wrong.

Michael

In message , Boomer
writes
On 10/15/2012 6:42 PM, W5DXP wrote:
On Monday, October 15, 2012 2:59:37 PM UTC-5, Boomer wrote:
(A G5RV) is not actually a bad antenna on 20 meters. However, the
performance on 75 is abysmal.

Would you please itemize the losses and radiation patterns that
explain why you believe that to be true for 75m?
--
73, Cecil, w5dxp.com

I don't have any of the math for you. However, I know what works and
what does not. You probably do not listen to your own G5RV. Its poor
performance is pretty clear to anyone who listens to you. However, if
you have an emotional bond with your G5RV, I would not want to be the
cause of any alienation in your relationship. Keep using it. The low
effective radiation makes for more band space for the rest of us. The
signal just disappears into the noise level.

Better yet just put up a random wire and a water pipe for ground. You
can get a perfect match with a tuner. It will work better than the long
wire the guy wanted to bury in the ground :-) In fact I recommend you
try burying your G5RV and make a stealth G5RV. It will still load with
a good tuner.

However, if you were actually interested in improving your transmitted
and received signal, you might tune around 75 and listen to those
stations putting out a big signal. Especially in the daytime when band
conditions are bad. Ask someone with that big signal what antenna they
are using. If they are using a G5RV then you are right and I am wrong.

I doubt if many will choose to use a G5RV when they can put up a
'better' antenna, and it's unlikely that the stations putting out really
big signals are using one. However, subject to an appreciation of its
characteristics and limitations, it can usually be made to perform
reasonably well.

Regarding the use of shorter-than-halfwave dipoles, the following
writings of W8JI (and the included links) are worth a read.
http://www.w8ji.com/short_dipoles_and_problems.htm

I've had a quick look, and it seems that the main cause of poor
efficiency/performance is that as the dipole is progressively shortened,
the increasingly high SWR causes high losses on the feeder. Cunningly
minimise the SWR, and you can still have a reasonably efficient
radiator.

It may also be useful to look at one of G4FGQ's programs - 'Dipole3'. If
you enter zero feeder lengths, this gives a quick assessment of the
efficiency of the dipole alone.
http://www.zerobeat.net/G4FGQ/page3.html
http://www.zerobeat.net/G4FGQ/dipole3.exe
--
Ian

On Tuesday, October 16, 2012 10:54:02 AM UTC-5, Boomer wrote:
I don't have any of the (G5RV) math for you.

Allow me to provide it based on EZNEC simulations and VK1OD's transmission line loss calculator. The G5RV will be compared to a 127 foot coax-fed dipole, both at a height of 40 feet and both antenna systems resonant at 3.72 MHz.

The 127 foot dipole has a maximum gain of 6.42 dBi at TOA of 90 degrees.
The G5RV dipole has a maximum gain of 6.06 dBi at TOA of 90 degrees.

The 127 foot dipole has a gain of 4.65 dBi at an elevation angle of 45 degrees.
The G5RV has a gain of 4.37 dBi at an elevation angle of 45 degrees.
The dipole beats the G5RV by 0.28dB

The 127 foot dipole has a resonant feedpoint impedance of 59 ohms at 3.72 MHz.
The G5RV has a feedpoint impedance of 33-j355 ohms at 3.72 MHz.

For 30' of RG-213, the 127' dipole has 0.093dB loss.
For 30' of 300 ohm twinlead, the G5RV has 0.89dB loss.
The 127' dipole beats the G5RV by 0.8dB

For another 50' of RG-213, the 127' dipole has 0.175dB loss.
For 50' of RG-213, the G5RV has 0.241dB loss.
The 127' dipole beats the G5RV by 0.066dB

The 127' dipole beats the G5RV by 1.15dB which is 20% of one S-unit. Human ears can barely detect a 1dB change.

So please explain to us how one signal that is 1.15dB lower than a second signal can "disappear into the noise level" and why your ears are so much better than the ears of normal homo sapiens.

Some hams think that -1.15dB on 75m (20% of one S-unit) is a rational compromise for an antenna that also works well as is on 40m, 20m, and 12m.
--
73, Cecil, w5dxp.com

On Tuesday, October 16, 2012 11:54:02 AM UTC-4, Boomer wrote:
On 10/15/2012 6:42 PM, W5DXP wrote:

On Monday, October 15, 2012 2:59:37 PM UTC-5, Boomer wrote:

(A G5RV) is not actually a bad antenna on 20 meters. However, the

performance on 75 is abysmal.



Would you please itemize the losses and radiation patterns that explain why you believe that to be true for 75m?

--

73, Cecil, w5dxp.com



I don't have any of the math for you. However, I know what works and

what does not. You probably do not listen to your own G5RV. Its poor

performance is pretty clear to anyone who listens to you. However, if

you have an emotional bond with your G5RV, I would not want to be the

cause of any alienation in your relationship. Keep using it. The low

effective radiation makes for more band space for the rest of us. The

signal just disappears into the noise level.



Better yet just put up a random wire and a water pipe for ground. You

can get a perfect match with a tuner. It will work better than the long

wire the guy wanted to bury in the ground :-) In fact I recommend you

try burying your G5RV and make a stealth G5RV. It will still load with a

good tuner.



However, if you were actually interested in improving your transmitted

and received signal, you might tune around 75 and listen to those

stations putting out a big signal. Especially in the daytime when band

conditions are bad. Ask someone with that big signal what antenna they

are using. If they are using a G5RV then you are right and I am wrong.



Michael

Random wire and water pipe was what got me hooked. Now I have lots of land behind my home for a real nice long wire but I cant get the wire across to my property