| Author |
Message |
    
Kc8gpd
Junior Member
Username: Kc8gpd
Post Number: 28
Registered: 2-2004
| | Posted on Saturday, May 22, 2010 - 4:46 pm: | 
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anyone know how well a full wave loop on 27mhz would work.
would be a full wave loop, 450 ladder line feeder of od a balanced HF tuner and a 1/4 wave ground/counterpoise off of the tuner ground.
it would be hung from the ceiling of a top floor apartment that has a wood/shingle roof and brick exterior siding.
i'm thinking the tuer and loop will eliminate most rfi issues and give me omnidirectional on the horizontal plane which should help with the noise floor and be good for dx as well as local propagation.
Rev. Robert P. Chrysafis
Universal Life Ministries (ULC)
http://www.ulc.org
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Tech237
Moderator
Username: Tech237
Post Number: 1343
Registered: 4-2004
| | Posted on Sunday, May 23, 2010 - 9:54 am: |
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I have not used a full wave loop on 27mHz, but have used one on 80m where it was a killer antenna (at my location). All I can say is try it and see..
Tech237
N7AUS
God only made some many perfect head, on the rest he put hair.
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Tech833
Intermediate Member
Username: Tech833
Post Number: 184
Registered: 12-2001
| | Posted on Monday, May 24, 2010 - 12:57 am: |
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It would be exactly like having a 2 element quad (like a Signal Engineering Skyhawk or an Avanti PDL2) laying on its back pointed UP.
On low frequencies like 80m, a loop has a desirable pattern by sending a lot of signal UP and nearly up so the ionosphere can reflect the signal back down. 27 MHz. does not reflect at the steep angles the lower frequencies do, so the signal pointed up would go right through the ionosphere layers and into space, never to be heard again.
For 27 MHz., you certainly want a lower takeoff angle than a loop will provide since 27 MHz. does not do NVIS well at all. In order to make a horizontal loop work well on 27 MHz., it would have to be at least a full wave above ground, preferably higher, with nothing under it.
Your radio 'Mythbuster' since 1998
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Kc8gpd
Junior Member
Username: Kc8gpd
Post Number: 29
Registered: 2-2004
| | Posted on Saturday, June 12, 2010 - 8:57 am: |
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how about crossed horizontal dipoles fed with balanced line and a tuner?
how would the 90 deg phasing be accomplished?
Rev. Robert P. Chrysafis
Universal Life Ministries (ULC)
http://www.ulc.org
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Tech833
Intermediate Member
Username: Tech833
Post Number: 197
Registered: 12-2001
| | Posted on Saturday, June 12, 2010 - 11:45 am: |
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ANY dipole low to the ground will radiate almost straight up. No good.
A dipole needs to be a minimum of 1/2 wave above ground (or metal roof, etc.) in order to work well at 27 MHz.
This research document describes it brilliantly, including pictures- http://www.arrl-sc.org/Tech%20Presentations/Near%20Vertical%20Incidence%20Sky%20Wave.doc
Your radio 'Mythbuster' since 1998
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Tech237
Moderator
Username: Tech237
Post Number: 1350
Registered: 4-2004
| | Posted on Saturday, June 12, 2010 - 11:00 am: |
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You do the 90 phasing by feeding one dipole with a section of line 1/4 wave longer than the other one.Robert if you want me to send you pdf files on indoor antennas, let me know and I can certainly do that for you.
Tech237
N7AUS
God only made some many perfect head, on the rest he put hair.
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Kc8gpd
Junior Member
Username: Kc8gpd
Post Number: 30
Registered: 2-2004
| | Posted on Sunday, June 13, 2010 - 12:26 am: |
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please do
kc8gpd (at) hotmail (dot) com
Rev. Robert P. Chrysafis
Universal Life Ministries (ULC)
http://www.ulc.org
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Ferd1605
Junior Member
Username: Ferd1605
Post Number: 39
Registered: 1-2005
| | Posted on Sunday, June 27, 2010 - 1:49 am: |
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i used a full wave loop inside on 27mhz many years ago and it worked great locally and a bit of skip also . at the time i lived on the upper floor of a old house that was made into a duplex and i had the upper story . what i did was used tacks and mounted it to a WALL , NOT the ceiling and fed it with 50ohm line with a 1/4 wave of 75ohm in the middle of one wall making it verticly polarized . it was bi-directional but i picked a wall to mount it on to make the best use of the directions i wanted to talk to . I was lucky that the ceilings were a bit over 8ft. and the loop was not quite a perfect square but close enough . it took a little tuning to get the perfect match but as i said , it worked VERY well for a indoor antenna and it didn't shoot UP and was verticly polarized .. |
Kc8gpd
Junior Member
Username: Kc8gpd
Post Number: 31
Registered: 2-2004
| | Posted on Tuesday, August 03, 2010 - 12:43 am: |
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i have maybe 7-1/2 ft ceilings here
can you email a diagram of your antenna design to the address above?
this may be a good hidden/low profile outdoor antenna.
Rev. Robert P. Chrysafis
Universal Life Ministries (ULC)
http://www.ulc.org
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Mikefromms
Senior Member
Username: Mikefromms
Post Number: 1023
Registered: 6-2003
| | Posted on Sunday, August 08, 2010 - 5:26 pm: |
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What about a sloper dipole on 11 meters? |
Mikefromms
Senior Member
Username: Mikefromms
Post Number: 1029
Registered: 6-2003
| | Posted on Tuesday, August 10, 2010 - 2:40 pm: |
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I am going to answer this one myself (my prior post above). I have built a 46 foot long double extended zep dipole that is supposed to have 3 dbd gain for 10, 11 meters. I needed something for 11 meters. Got it up today. It is working without the need for a tuner on 11 and 10 meters. SWR goes up as you go down below cb band and continues downward as you go up above cb. It is usable for 10 and 11 meters. It is around 1.4 on 27.385 where I did my measurements. I'm only abut 1/4 wavelength off the ground in a slope style position for the antenna. It is receiving signals very good. Can't test it out until we have some conditions. Well, I guess I could holler at some truckers.... |
Mikefromms
Senior Member
Username: Mikefromms
Post Number: 1030
Registered: 6-2003
| | Posted on Tuesday, August 10, 2010 - 2:43 pm: |
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But let me chime in on the full wave loop for cb band: If you can get the loop to stand up so you can run it as a vertical at about 18 feet at its bottom, you should have about 2 DBD favoring the broadside. I have found that when folks say something won't work it pays to try it anyway. I have disproved book and the experts on several occasion. Build it and try it. However, I'd be careful of any antenna indoors.
Mikefromms |
