looking for some opinions on uhf reapeater antennas and reasons why you like one over the other.
im using a fiberglass omni currently. the repeater is located on the south shore of Long Island. i have no desire for tx rx to the south because its the Atlantic ocean. so my tx rx need only be north west and east. is it posable to set up something like a 4 or 8 bay dipole configured for a N W E patern only?
UHF repeater antenna...... fiberglass omni or dipole???
Moderator: Queue Moderator
-
FF/EMT/KC2NFB
- Posts: 108
- Joined: Thu Oct 14, 2004 3:13 pm
- What radios do you own?: Way too many to list, over 50
-
Birken Vogt
- Posts: 262
- Joined: Thu Nov 10, 2005 7:53 pm
Look at this page
http://www.andrew.com/products/antennas ... 22-000.pdf
Look down to the DB404L mounted with elements toward the tower (assuming you are using a tower). It nulls out the one side pretty good.
I like the exposed dipoles because I think they must give a little better protection from lightning since the central mast, which is capped with a lightning rod clamp, should carry the current rather than having to carry it through the antenna itself as in the case of a fiberglass antenna. But I think that is probably a relatively minor issue.
Birken
http://www.andrew.com/products/antennas ... 22-000.pdf
Look down to the DB404L mounted with elements toward the tower (assuming you are using a tower). It nulls out the one side pretty good.
I like the exposed dipoles because I think they must give a little better protection from lightning since the central mast, which is capped with a lightning rod clamp, should carry the current rather than having to carry it through the antenna itself as in the case of a fiberglass antenna. But I think that is probably a relatively minor issue.
Birken
-
Dan562
- Posts: 533
- Joined: Mon Aug 23, 2004 7:30 pm
- What radios do you own?: Kenwood, Yaesu, ICOM, Motorola
On the Celwave Fiberglass verticals there's a Parasitic Reflector Element that can be purchased and installed on the main antenna. This allows the Fiberglass vertical to produce a cardiod radiation pattern when being mounted at the top of a tower or building structure. These are used on or near Chicago's lakefront two-way transmitter sites.
The main heavy duty Fiberglass verticals being Celwave, DB Products and Sinclair all have superior metal grounding top (caps) to help disappate the "Static" build up on these antennas. As far as direct lightning strikes to antennas, the antenna installation should always have Cad Welded Grounding Wire / Rods at the base of the tower and/or be Cad Welded into the Roof Top Grounding Grid and into the "I" Beams of the building.
The use of commercially manufactured Polyphasers or equivalent "Static / Lightning Protectors" connected to the Heliax Coaxial Feedline prior to entering into the building using large copper insulated plates and Cad Welded to the building's grounding system.
The main heavy duty Fiberglass verticals being Celwave, DB Products and Sinclair all have superior metal grounding top (caps) to help disappate the "Static" build up on these antennas. As far as direct lightning strikes to antennas, the antenna installation should always have Cad Welded Grounding Wire / Rods at the base of the tower and/or be Cad Welded into the Roof Top Grounding Grid and into the "I" Beams of the building.
The use of commercially manufactured Polyphasers or equivalent "Static / Lightning Protectors" connected to the Heliax Coaxial Feedline prior to entering into the building using large copper insulated plates and Cad Welded to the building's grounding system.
You stated that you're on the south shore of Long Island. If corrosion from salt air is a problem in your area, you may wish to consider an fiberglass enclosed antenna from a longevity standpoint. The exposed dipoles are fine as long as they're not used in a heavily corrosive environment(i.e. industrial, salt spray).
-
FF/EMT/KC2NFB
- Posts: 108
- Joined: Thu Oct 14, 2004 3:13 pm
- What radios do you own?: Way too many to list, over 50
ok. so im going to stay with the omni fiberglass. i want to up the gain. im thinking of using an Andrew Decibel ASP705K. take a look:
http://www.tessco.com/products/displayP ... entPage=12[/url][/url]
with this antenna total hight will be 65 feet from tip to see level with 50 watts in to the antenna. the ERP if my calculations are correct will be 500 watts. the repeater area terrain is totaly flat. im looking to achieve 5 mi coverage on 4 watt HT's.
what do you think?[/url]
http://www.tessco.com/products/displayP ... entPage=12[/url][/url]
with this antenna total hight will be 65 feet from tip to see level with 50 watts in to the antenna. the ERP if my calculations are correct will be 500 watts. the repeater area terrain is totaly flat. im looking to achieve 5 mi coverage on 4 watt HT's.
what do you think?[/url]
-
Dan562
- Posts: 533
- Joined: Mon Aug 23, 2004 7:30 pm
- What radios do you own?: Kenwood, Yaesu, ICOM, Motorola
System Coverage???
In what application are you using these 4 Watt Subscriber units ... Just with a Base Station or Base Station / Repeater System?
If in a Base Station / Repeater System:
What type of Duplexers?
What type of Coax or Heliax RF Feedline are you intending to use?
Is your system located in and among:
1. High Downtown Buildings?
2. Buildings that are 4 stories (45 Feet) or less?
3. Residential Areas?
What is the typical (Summer) Foliage like for Trees and Bushes?
When using the 4 Watt Handheld Subscriber units:
1. Do you intend to use them (TX & RX) at Head level?
2. Or worn and used (TX & RX) at Waist Level with an External SPKR/MIC?
a. Using a 1/4 Wave Whip (6") antenna?
b. Using a Heliflex Stubby (3") antenna?
If in a Base Station / Repeater System:
What type of Duplexers?
What type of Coax or Heliax RF Feedline are you intending to use?
Is your system located in and among:
1. High Downtown Buildings?
2. Buildings that are 4 stories (45 Feet) or less?
3. Residential Areas?
What is the typical (Summer) Foliage like for Trees and Bushes?
When using the 4 Watt Handheld Subscriber units:
1. Do you intend to use them (TX & RX) at Head level?
2. Or worn and used (TX & RX) at Waist Level with an External SPKR/MIC?
a. Using a 1/4 Wave Whip (6") antenna?
b. Using a Heliflex Stubby (3") antenna?
-
FF/EMT/KC2NFB
- Posts: 108
- Joined: Thu Oct 14, 2004 3:13 pm
- What radios do you own?: Way too many to list, over 50
-
FF/EMT/KC2NFB
- Posts: 108
- Joined: Thu Oct 14, 2004 3:13 pm
- What radios do you own?: Way too many to list, over 50
-
Tom in D.C.
- Posts: 3859
- Joined: Tue Sep 04, 2001 4:00 pm
- What radios do you own?: Progreso soup can with CRT
Repeater on LI...
Question: What power limitation is shown on your license? 500W ERP at 50 feet HAAT is going to get out a LOT farther than 4 or 5 miles. I'd be willing to bet I
could hear that signal all the way up on the North Shore with no problem when
you get the machine up and running.
If some other agency shares your frequency, say up in Connecticut or down the Jersey shore, you could have problems in both directions with the setup you're contemplating.
I'm originally from East Rockaway and I know your area's RF conditions. I was
able to work a good 50 miles years ago on VHF AM with 5 watts and a unity
gain groundplane located in the attic.
could hear that signal all the way up on the North Shore with no problem when
you get the machine up and running.
If some other agency shares your frequency, say up in Connecticut or down the Jersey shore, you could have problems in both directions with the setup you're contemplating.
I'm originally from East Rockaway and I know your area's RF conditions. I was
able to work a good 50 miles years ago on VHF AM with 5 watts and a unity
gain groundplane located in the attic.
Tom in D.C.
In 1920, the U.S. Post Office Department ruled
that children may not be sent by parcel post.
In 1920, the U.S. Post Office Department ruled
that children may not be sent by parcel post.
I have a heavy duty celwave that took a direct hit, the top cap has a arc scar and the antenna no longer has DC contunity to the mount. The strike also blew the 1/2 jumper connector at the connnection to the 7/8. The system has Polyphaser protectors mounted in a well grounded protector plate. A computer monitor in the transmitter room had to be degaused several times due to the field this strike imposed on the radio room ground wires. The Quantar that is on this antenna was not damaged.The main heavy duty Fiberglass verticals being Celwave, DB Products and Sinclair all have superior metal grounding top (caps) to help disappate the "Static" build up on these antennas. As far as direct lightning strikes to antennas, the antenna installation should always have Cad Welded Grounding Wire / Rods at the base of the tower and/or be Cad Welded into the Roof Top Grounding Grid and into the "I" Beams of the building.
As to high gain (50 watts in 500 ERP) you may not get the close in coverage with this setup. Look at the antenna patterns, the high gain antennas have almost no coverage under the tower but are great 50 miles away.
I also have a system on the South Shore of LI and found a 3 to 5 DB antenna at 100 feet covers better than a 10DB in the local area. Our CoChannel in New Jersey still hears us either way. Do not get carryed away with Gain, sometimes it can hinder rather than help.
Cause Motorola said so that's why
Re: Repeater on LI...
What frequency is this?Tom in D.C. wrote:If some other agency shares your frequency, say up in Connecticut or ...
"I'll eat you like a plate of bacon and eggs in the morning. "
- Some loser on rr.com
eBay at it's finest:
Me: "What exactly is a 900Mhz UHF CB?"
Them: "A very nice CB at 900Mhz speed!"
- Some loser on rr.com
eBay at it's finest:
Me: "What exactly is a 900Mhz UHF CB?"
Them: "A very nice CB at 900Mhz speed!"
Has anyone tried using the Bluewave antennas? I'm looking at the Summit folded dipole series and they look VERY heavy-duty.
For VHF we use mainly BA1010s and 620 super heavy-duty fiberglass antennas at mountaintop sites because they're the only antennas that stay up through years of heavy rime ice buildup. However these Bluewave antennas appear to be well built for heavy ice loading conditions (on paper anyway)...
http://www.bluewaveantenna.com/products/summit.html
For VHF we use mainly BA1010s and 620 super heavy-duty fiberglass antennas at mountaintop sites because they're the only antennas that stay up through years of heavy rime ice buildup. However these Bluewave antennas appear to be well built for heavy ice loading conditions (on paper anyway)...
http://www.bluewaveantenna.com/products/summit.html
Casey KJ7XE
-
Dan562
- Posts: 533
- Joined: Mon Aug 23, 2004 7:30 pm
- What radios do you own?: Kenwood, Yaesu, ICOM, Motorola
Analog RF System Coverage
Hello Devin,
Here’s what I would suggest to do so with your Fiberglass +10 Gain Antenna idea ... change it to a lessor amount of Omni Directional Gain some thing around +5~6 dB Gain Maximum. Using a +10 dB Omnl Gain antenna is an over kill for the RF system coverage you’re requesting and probably would cause more co-channel interference that you do not want or need.
I’ve based my Path Losses upon the information that you have provided, with the two exceptions the antenna and the feedline. I used only a +5 dB Omni Directional Gain Fiberglass antenna rated at 150 RF Watt Power Level because of the RF 50 Watt Transmitter Output Level. You do not need an antenna that is RF rated at 500 Watts unless you were using a 250~350 Watt RF Output Power transmitter; and then it would be still questionable because of RF Losses through Duplexers, Circulators and Heliax Feedlines. I also changed the Heliax from 7/8” to ½” because the RF system does not require the larger coaxial cable to reduce losses only by .5 dB maximum! You could not detect that little amount of signal difference when using the system.
Building Losses.......................................................-10 dB
Foliage (Tree & Bushes).........................................- 6 dB
Subscriber at Waist Level & Stubby Ant...............-13 dB
Duplexers.................................................................- 2 dB
1/2" Heliax Feedline...............................................- 1 dB
Total Losses............................................................-32 dB
+5 dB Gain Celwave PD201....................................+ 5 dB
Repeater's Rcvr Sens: .25uV@12dB SINAD............+ 6 dB
Total Gain..................................................................+11 dB
Total RF System Losses.............................................-21 dB
UHF Repeater RF Output 50 Watts, Antenna @ 60 Feet
The RF Analog System Coverage is based upon the older /\/\ system coverage calculator which many technical people may disagree with and rightfully so with their opinion if they have the latest and greatest RF coverage software programs.
The following coverage provides you with an idea how well the Subscribers units will access the UHF Repeater:
90%/10% This indicates the Subscriber units will be able to access the UHF Repeater Coverage 90% of the time with a 10% chance of Dead Spots / No Access Probably.
70%/30% This indicates the Subscriber units will be able to access the UHF Repeater Coverage 70% of the time with a 30% chance of Dead Spots / No Access Probably.
50%/50% This indicates the Subscriber units will be able to access the UHF Repeater Coverage 50% of the time with a 50% chance of Dead Spots / No Access Probably.
90% RF System Coverage Radius from the Repeater is 6.5 Air Miles
70% RF System Coverage Radius from the Repeater is 9.8 Air Miles
50% RF System Coverage Radius from the Repeater is 14.2 Air Miles
Another alternative would be to use a +3 dB Omni Directional Gain antenna and decrease the RF System Coverage to:
90% RF System Coverage Radius from the Repeater is 5.5 Air Miles
70% RF System Coverage Radius from the Repeater is 8.6 Air Miles
50% RF System Coverage Radius from the Repeater is 12.2 Air Miles
Dan
Here’s what I would suggest to do so with your Fiberglass +10 Gain Antenna idea ... change it to a lessor amount of Omni Directional Gain some thing around +5~6 dB Gain Maximum. Using a +10 dB Omnl Gain antenna is an over kill for the RF system coverage you’re requesting and probably would cause more co-channel interference that you do not want or need.
I’ve based my Path Losses upon the information that you have provided, with the two exceptions the antenna and the feedline. I used only a +5 dB Omni Directional Gain Fiberglass antenna rated at 150 RF Watt Power Level because of the RF 50 Watt Transmitter Output Level. You do not need an antenna that is RF rated at 500 Watts unless you were using a 250~350 Watt RF Output Power transmitter; and then it would be still questionable because of RF Losses through Duplexers, Circulators and Heliax Feedlines. I also changed the Heliax from 7/8” to ½” because the RF system does not require the larger coaxial cable to reduce losses only by .5 dB maximum! You could not detect that little amount of signal difference when using the system.
Building Losses.......................................................-10 dB
Foliage (Tree & Bushes).........................................- 6 dB
Subscriber at Waist Level & Stubby Ant...............-13 dB
Duplexers.................................................................- 2 dB
1/2" Heliax Feedline...............................................- 1 dB
Total Losses............................................................-32 dB
+5 dB Gain Celwave PD201....................................+ 5 dB
Repeater's Rcvr Sens: .25uV@12dB SINAD............+ 6 dB
Total Gain..................................................................+11 dB
Total RF System Losses.............................................-21 dB
UHF Repeater RF Output 50 Watts, Antenna @ 60 Feet
The RF Analog System Coverage is based upon the older /\/\ system coverage calculator which many technical people may disagree with and rightfully so with their opinion if they have the latest and greatest RF coverage software programs.
The following coverage provides you with an idea how well the Subscribers units will access the UHF Repeater:
90%/10% This indicates the Subscriber units will be able to access the UHF Repeater Coverage 90% of the time with a 10% chance of Dead Spots / No Access Probably.
70%/30% This indicates the Subscriber units will be able to access the UHF Repeater Coverage 70% of the time with a 30% chance of Dead Spots / No Access Probably.
50%/50% This indicates the Subscriber units will be able to access the UHF Repeater Coverage 50% of the time with a 50% chance of Dead Spots / No Access Probably.
90% RF System Coverage Radius from the Repeater is 6.5 Air Miles
70% RF System Coverage Radius from the Repeater is 9.8 Air Miles
50% RF System Coverage Radius from the Repeater is 14.2 Air Miles
Another alternative would be to use a +3 dB Omni Directional Gain antenna and decrease the RF System Coverage to:
90% RF System Coverage Radius from the Repeater is 5.5 Air Miles
70% RF System Coverage Radius from the Repeater is 8.6 Air Miles
50% RF System Coverage Radius from the Repeater is 12.2 Air Miles
Dan
-
FF/EMT/KC2NFB
- Posts: 108
- Joined: Thu Oct 14, 2004 3:13 pm
- What radios do you own?: Way too many to list, over 50
-
FF/EMT/KC2NFB
- Posts: 108
- Joined: Thu Oct 14, 2004 3:13 pm
- What radios do you own?: Way too many to list, over 50
-
Birken Vogt
- Posts: 262
- Joined: Thu Nov 10, 2005 7:53 pm
FWIW I prefer Celwave exposed dipoles when they are available...at least I did prefer them...what with all the mergers/buyouts it is never sure who owns what any more or if it is even made...anyway the things I like about the Celwave are that the center conductor portion of the dipole element points down instead of up...gives a little more edge on lightning in my book to have the grounded portion up...and also the harness is run inside the mast...and also the hardware is quite a bit thicker/heavier. But they make no UHF antenna that I am aware of, this is all high band I am speaking of, for general reference.
Birken
Birken