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antenna experiment


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#1 JohnE

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Posted 25 February 2016 - 09:30 PM

will be conducting an antenna experiment w/575 machine in the near future to see if there is any real difference in pattern and range vs cost.  RSSI readings at fixed locations have been taken this week. waiting for the Comtelco antenna to show up.

all things being equal the only change will be the antenna itself.

the antennas will be a Laird 5dBd($150) currently in service

Comtelco 6dbd ($200)

PD 201 5 dBd ($450)

the Laird is physically the smallest one, the other 2 are roughly the same size/weight.

will post pics of the 3 together.

not looking for radical results but it should be interesting.

ground elevation ~150'

structure ~200'


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#2 6040

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Posted 26 February 2016 - 04:17 AM

I'm tuned in. I happen to have the 6dbd Comtelco. Got burned though, didnt do my home work and bought it straight from Comtelco only to find out I could have saved a hondo from one of thier vendors!

oh well, hopefully it compares well in your comparison so it takes some of my sting away...LOL



#3 n4gix

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Posted 26 February 2016 - 09:04 AM

I will be following closely myself, as I know my next expense will be new Superflex and antenna for my new Bridgecom repeater. There's no point at all in putting used tires on a new car! :lol:



#4 JohnE

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Posted 26 February 2016 - 05:09 PM

I will be following closely myself, as I know my next expense will be new Superflex and antenna for my new Bridgecom repeater. There's no point at all in putting used tires on a new car! :lol:

agreed

how long is the cable run?


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#5 JohnE

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Posted 26 February 2016 - 05:12 PM

I'm tuned in. I happen to have the 6dbd Comtelco. Got burned though, didnt do my home work and bought it straight from Comtelco only to find out I could have saved a hondo from one of thier vendors!

oh well, hopefully it compares well in your comparison so it takes some of my sting away...LOL

I call them directly and did not pay what they showed on their web page. it was actually less than what their vendors sell it for.

also just for the record I have one already and have been happy w/results I'm getting.


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#6 RF Medic

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Posted 29 February 2016 - 09:49 PM

D***   lairds...nothing but 200watt dummy loads


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#7 JohnE

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Posted 16 March 2016 - 06:36 PM

the new antenna is here and here are some pics of the 3 antennas I will bu using.

L-R

Laird, Comtelco, RFS

IMG_0226_zpsbicbvuwz.jpg

ID tags on the antennas

IMG_0229_zpsw7pyn4ro.jpg

IMG_0230_zps0zmcfqwk.jpg

IMG_0231_zpsmolw5drl.jpg

for the record the machine is currently running a Laird like the one in the pics, I just used this one as a reference to the others.

hope to put up the Comtelco on Friday weather permitting.

one other interesting point on these, the Comtelco is not DC grounded the other 2 are.


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#8 JohnE

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Posted 23 March 2016 - 06:27 PM

swap 1 made to the Comtelco

as an added side note the VSWR for the Laird was 1.3 and the Comtelco was 1.65.


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#9 ASRM

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Posted 27 March 2016 - 06:31 AM

Our shop has a slew of the Laird's (10+ in stock), I am thinking about using one for our new 675 repeater that we hope will go up in a month or 2, after the new tower and my experimental build of a Johnson PPL6000. I have been hearing really good things on the Laird's.



#10 mainehazmt

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Posted 28 March 2016 - 05:53 PM

Send your rejected ones to me. Your worst is prob better than my best lol

Btw is there a way besides an antenna analyzer to see if an antenna is good? I have an older business band uhf that I have no clue about
Don't want to install it and find out it isn't any good

#11 n4gix

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Posted 28 March 2016 - 08:11 PM

Sure! A $3000 spectrum analyzer with tracking generator and a VSWR bridge...



#12 Corey

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Posted 28 March 2016 - 09:28 PM

Sure! A $3000 spectrum analyzer with tracking generator and a VSWR bridge...

 

Send your rejected ones to me. Your worst is prob better than my best lol

Btw is there a way besides an antenna analyzer to see if an antenna is good? I have an older business band uhf that I have no clue about
Don't want to install it and find out it isn't any good

 

 

I would think the cheaper way would be to bolt it to something stable like a metal fence or just stand it up on a mast. Once you find a way to stand it up hook up a radio and an SWR meter and see what you get. How ever you test in be sure it has ample free space and don't get to close to it well keying it up. You may ask around and see if any of your fellow hams have an Anritsu Site Master and if so can you get them to sweep it for you.

 

Corey


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Just My $.02

 

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#13 Corey

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Posted 28 March 2016 - 09:41 PM

swap 1 made to the Comtelco

as an added side note the VSWR for the Laird was 1.3 and the Comtelco was 1.65.

 

John,

 

Ever tried any of the dipoles on your repeater? I run a DB404-B on my base, DB411-B as the TX antenna and a DB413-B as the RX on my commercial UHF DMR system, I am getting ready to upgrade my other commercial site to a Duplexed DB408-B and my GMRS repeater runs a Duplexed DB420-B. I don't have a single bad thing to say about any of them. I do have some choice words about a few of the fiberglass sticks I have used over the years.

 

Corey


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Just My $.02

 

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#14 jvfreetage

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Posted 29 March 2016 - 03:37 AM

I would think the cheaper way would be to bolt it to something stable like a metal fence or just stand it up on a mast. Once you find a way to stand it up hook up a radio and an SWR meter and see what you get. How ever you test in be sure it has ample free space and don't get to close to it well keying it up. You may ask around and see if any of your fellow hams have an Anritsu Site Master and if so can you get them to sweep it for you.

Corey

I agree with Corey.

Just remember, a dummy load has a 1.0:1 SWR. SWR just makes the radio happy. Your field strength meters and just testing the thing is going to give you your best findings.

HAPPY HUNTING!

James

#15 JohnE

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Posted 29 March 2016 - 06:36 PM



Sure! A $3000 spectrum analyzer with tracking generator and a VSWR bridge...

I have an Agilent antenna/cable analyzer and a General Dynamics service monitor w/most of the options.

this is just a field test for the real world for S's and G's to compare if $$$$$ antenna performs as well as the $$ antenna.


 

Ever tried any of the dipoles on your repeater? I run a DB404-B on my base, DB411-B as the TX antenna and a DB413-B as the RX on my commercial UHF DMR system, I am getting ready to upgrade my other commercial site to a Duplexed DB408-B and my GMRS repeater runs a Duplexed DB420-B. I don't have a single bad thing to say about any of them. I do have some choice words about a few of the fiberglass sticks I have used over the years.

I have never cared for exposed dipole arrays as I have had too many water intrusion issues w/them. I had a DB 411 and gave it to one of Rich's buddies

I have had some manufacturing issues w/fiberglass antennas. radomes coming out of the support pipes but those were Irene and Sandy related.

kcc006.jpg

kcc003.jpg


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#16 Corey

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Posted 30 March 2016 - 05:55 AM

So far I have not had any issues with the Andrew / Comscope DB line of dipoles. The DB420-B on my GMRS site is over 10 years old and still works as good as day it was put into service. I have herd others complain about some of the DB knockoffs failing in the field but never any bad words about the real deal dipoles.

 

That is crazy how the antenna separated at the mount, must have been some crazy wind! My issue with past fiberglass was the gelcoat weathering and water soaking into the glass mat causing huge drops in performance. Your would be the first one I have seen sheer off at the mounting tube. Whats the broadcast antenna stack in the background?


Just My $.02

 

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#17 JohnE

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Posted 30 March 2016 - 07:26 AM

college FM broadcast.


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#18 n4gix

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Posted 30 March 2016 - 09:29 AM

Irene's and Sandy's winds surely must have far exceeded the wind-loading design for those fiberglass antennas...



#19 zap

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Posted 30 March 2016 - 01:25 PM

RFI builds a sweet (fully welded) exposed dipole array that's worth checking out if you have some money to burn.

DB's water intrusion issues were mostly settled by 2005. Know of a 224 suffering from it currently.

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#20 mainehazmt

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Posted 30 March 2016 - 06:55 PM

I would think the cheaper way would be to bolt it to something stable like a metal fence or just stand it up on a mast. Once you find a way to stand it up hook up a radio and an SWR meter and see what you get. How ever you test in be sure it has ample free space and don't get to close to it well keying it up. You may ask around and see if any of your fellow hams have an Anritsu Site Master and if so can you get them to sweep it for you.
 
Corey

have to wait till the snow is gone lol.

Ps sorry for the hijack. John




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