Repeater Antenna?

[taco6513]

I am in process of setting up my second repeater.

This will be on top of a 200ft free standing solid rod tower sitting on a small hill. (if it matters)

The antenna will be on top of tower.

 

I have two antenna choices:

 

The DB420 and a DB413

 

Which would be best? The DB413 has a offset pattern. This would be fine as I want more coverage West

as I have my other repeater that has coverage East. The DB420 has a gain of 9.2 with 16 folded dipoles.

The DB413 has a gain of 12.4 with 8 folded dipoles.

 

I have both antennas. I am thinking the DB413 with the higher gain? 

 

Any options?? or advise would be great.

 

Thanks

WRCW870

KI5GXD

[Radioguy7268]

It appears that the DB413 is listed as having 'either' 14 or 24 MHz bandwidth - and the DB413B is what would cover 450 to 470.  Do you have the ability to sweep the antennas for response?

 

Either model number is a good choice, the better choice IMHO is the one that sweeps the best (assuming they're both used). The dB difference between them will be seen more on talk out than talk back - and the receive side is where most Repeater systems fall short.

[gortex2]

As said Id sweep both antenna's for return loss on the frequency you plan to use. Id use the best of the 2. They are both solid performers. The only issue with more gain is if its really higher than surrounding area. I have 1 at 2500' and have some dead spots heading down the mountain until I get 5 miles away. 

[NCRick]

Hope I am not thread jacking but I'm wondering if the 20 foot above "structure or tree to which it is mounted " rule i though I understood comes into play with repeaters?  Is there separate rules or is a tower considered a structure?  Thanks!  Repeaters are really cool and I'm totally curious. 

[BoxCar]

The 6.1 meter or 20 foot rule means the structure is not subject to registration. Towers and poles greater than 20 feet in height are usually listed on the license as the transmitter location. This primarily applies to services where individual frequencies are required to be coordinated which isn't needed for personal or amateur communications. There are other rules that apply such as being near an airport or lighting for antennas more than 20 feet in height.

[mbrun]

Hope I am not thread jacking but I'm wondering if the 20 foot above "structure or tree to which it is mounted " rule i though I understood comes into play with repeaters? Is there separate rules or is a tower considered a structure? Thanks! Repeaters are really cool and I'm totally curious.

The rigid 20’ rule was removed in the 2017 (current) version of the Part 95 rules, either accidentally or on purpose. Paragraph 95.1741 now covers antenna height. That paragraph redirects to 95.317 where it is described that antenna structures of 200’ or more may require FAA registration and where restrictions on antenna heights near airports are described.

 

 

Michael

WRHS965

KE8PLM

[NCRick]

That's cool!  Thanks folks.  I guess it's time for me to think about a tech license or something.  I'm finding it all interesting.

[berkinet]

... rule i though I understood comes into play with repeaters? ...

 

Adding to the answers above, there is nothing different about a repeater. It is still a single antenna and subject to the same rules (or lack thereof) as any other GMRS station. About the only difference in a repeater antenna is if it is used with a duplexer, in which case you need to be sure the antenna design will provide good response on both transmit and receive. But, of course, that has nothing to do with where or how the antenna is mounted.

[taco6513]

I will have them both tested and make my decision.

 

Thank you for the advise.

 

WRCW870

[gman1971]

If you live in a very rough terrain area, high gain will be very detrimental. I found that going with lower gain (as in Laird FG4500 unity gain antenna) gave me overall better performance than a 4dBd Hustler G6.... so keep that in mind.

 

G.

[WQBU369]

If you live in a very rough terrain area, high gain will be very detrimental. I found that going with lower gain (as in Laird FG4500 unity gain antenna) gave me overall better performance than a 4dBd Hustler G6.... so keep that in mind.

 

G.

[WQBU369]

So youre saying if i live in a area with alot of trees and hills unity gain is the way to go ?