Batboard

I have a UHF repeater that has less then stellar in-building coverage as the antenna is on the roof. We would like to delploy a Radiax system, using a power divider (25% to radiax, 75% to the antenna)

Kathrein-Scala has several models, but they are 50% to each port. Any ideas on a manufacturer who can produce a 25/75 divider?

Call EMR... I think they can build custom dividers like that.

We had Sinclair build us custom power dividers in the past. They do work as advertised, but be aware they have fairly high loss compared to the 50/50 splitters.

Todd

spareparts wrote:I have a UHF repeater that has less then stellar in-building coverage as the antenna is on the roof. We would like to delploy a Radiax system, using a power divider (25% to radiax, 75% to the antenna)

Why are you making it hard on yourselves? Go for a 50/50 split - those are easy to design a power divider for.

Remember, the difference between 50% and 75% is only an increase of 1.7dB. One S unit is nominally 6 dB.

I think you'd be better off with 50/50 anyway. Go for that.

Why do you need an antenna on top of the building to talk inside the building???

Move the repeater to one third building elevation, feed 50% up to
the top floor, and the other 50% down into the basement.
Don't forget the load on each end of the Radiax.

The system needs to cover the town around the building, and provide in-building coverage.

You might gain more by changing the antenna to one that has built-in downtilt (.05 or 1 degree) rather than installing radiax. You also won't loose your system gains when trying to cover areas other than the building. Here is a UHF antenna that has 3 degree DT:

http://www.rfsworld.com/websearch/DataS ... ?q=455DT3D

KS4VT wrote:You might gain more by changing the antenna to one that has built-in downtilt (.05 or 1 degree) rather than installing radiax. You also won't loose your system gains when trying to cover areas other than the building. Here is a UHF antenna that has 3 degree DT:

http://www.rfsworld.com/websearch/DataS ... ?q=455DT3D

WAY too much gain.. use a unity gain true dipole antenna. That will help to fill in below the antenna. We use the Comtelco BSL450-C for 450 to 470 or the BSL450-BC for 445-465.

Put the repeater near the one half height of the building, 50% up the radiax with the Comtelco BSL450-C on the end, the other 50% down the radiax to the basement.

One building we did has a 10db yagi antenna on 462 pointed down inside the building from a couple of floors below the top. It works well in the building and even out a couple of miles. 13 story building IIRC.

I only used that antenna as an example. I have no idea how big the "town" is to cover so I SWAG'ed it.

Just use a -10dB directional coupler. Then it's 10W in the building and 90W out the antenna...

A -20dB directional coupler might even be just as effective, and potentially easier to source. Route the output to a small amp and you're in business. If you transmit 100W, the coupler will shear off 1W, leaving 99W to be sent up to the roof, and the 1W signal can be used to drive a 5-10W amp for inbuilding.

I would think that 1W into a piece of radiating coax should be enough. 5W ought to be.

SlimBob wrote:Just use a -10dB directional coupler. Then it's 10W in the building and 90W out the antenna...

A -20dB directional coupler might even be just as effective, and potentially easier to source. Route the output to a small amp and you're in business. If you transmit 100W, the coupler will shear off 1W, leaving 99W to be sent up to the roof, and the 1W signal can be used to drive a 5-10W amp for inbuilding.

I would think that 1W into a piece of radiating coax should be enough. 5W ought to be.

But you would loose the ability to use the radiax section for increased talk-back because the proposed 5-10 watt building amp is not bi-directional. You may hear the call but may have one heck of the time responding back.

KS4VT wrote: But you would loose the ability to use the radiax section for increased talk-back because the proposed 5-10 watt building amp is not bi-directional. You may hear the call but may have one heck of the time responding back.

True enough.

Try Scala Electronic Corporation in Medford, Oregon. Telephone # 503 - 779 - 6500, they manufacture several versions:

PD2 - 55 50% - 50%
PD2 - 72 75% - 25%
PD2 - 91 90% - 10%

I've used all three of these with Radiax in the Radio Paging and Two-way Radio applications with great success.

Dan

Nice to see you back on the board dan, you are always a wealth of information!

Dan562 wrote:Try Scala Electronic Corporation in Medford, Oregon. Telephone # 503 - 779 - 6500, they manufacture several versions:

Thanks! Will call Monday AM

Ended up ordering a SP-12974 – PDL2/91/50 Power from Kathrein Scala Corporation. $440.00

Whoa, those Power Dividers have certainly increased in price. They used to cost about $100.00 each, talk about inflated prices Geesh! They must have spoken to the financial people at the Motorola's Schaumburg Campus!

Well at you were able to get what you needed ..... a Gold Plated RF Power Divider.

Dan

Dan562 wrote:Well at you were able to get what you needed ..... a Gold Plated RF Power Divider.

Per Don Bennett @ Kathrein-Scala, it's just gold anodized ......