Building a antenna

[yankees6161]

Any one here ever build there own antenna? I’m thinking about building a yagi style antenna tuned to 800mhz. Looking for info of materials needed and how to properly tune. Any help will be greatly appreciated.

 

[mmckenna]

I've built a few.

I built a 6 meter beam out of copper pipe.
I've built a 2 meter beam out of welding rod and PVC pipe.
I built a UHF beam out of PVC pipe and an old tape measure.

The UHF beam used a hairpin tuning arrangement. I used one of the NanoVNA's to tune it and some careful trimming of the elements.

 

[prcguy]

Unless you have an antenna analyzer to test and tune the antenna, an 800MHz Yagi is not a good candidate for a first time antenna project. If you simply copied instructions found online there are way too many mistakes that can be made because of the high frequency range and very small dimensions involved. Its not like making an HF antenna or even a VHF antenna where a 1/8" mistake here or there is not a big deal. There are plenty of good inexpensive factory made and tested 800MHz Yagis available on eBay that are cheap.

Any one here ever build there own antenna? I’m thinking about building a yagi style antenna tuned to 800mhz. Looking for info of materials needed and how to properly tune. Any help will be greatly appreciated.

 

[GROL]

Any one here ever build there own antenna? I’m thinking about building a yagi style antenna tuned to 800mhz. Looking for info of materials needed and how to properly tune. Any help will be greatly appreciated.

I have made plenty of antennas, but when I found some of the celluar yagis on eBay at cheap prices I bought one. One example.

Outdoor Yagi Antenna Directional 700/800/850/900MHz 4G LTE AT&T Verizon T-Mobile | eBay

What is the difference of different outdoor antennas?. If the outdoor signal is weak, you need the outdoor directional antenna which should be pointed to the base station to get signal, such as the outdoor yagi antenna, the outdoor LPDA antenna, etc.

www.ebay.com

 

[yankees6161]

GROL,
They are cheap
Did it meet your expectations?

 

[GROL]

GROL,
They are cheap
Did it meet your expectations?

I bought one exactly like that one. It does improve signal, but unfortunately it didn't help my application. I was trying to overcome the simulcast issue, but I could not get enough rejection from the other sites as I am so close to all of them. I did get a bit of improvement by mounting it horizontally instead of vertical to reduce overall signal level. It boosted signal to a more usable level for the county over from me, but that one too is simulcast and I still had issues because those sites were mostly all in the same general direction. I finally had to get an SDS100. You would need to convert that connector to BNC or SMA. I would suggest a short pigtail to BNC or SMA. I found a short female N to BNC cable on Amazon for a few dollars. I can make cables, but don't like to especially if the cable is as cheap as the connectors themselves. It looks like it is an N connector like the one I bought. Back when I bought mine there were some cheap higher gain versions that are longer, but I don't see those listed now.

I recently moved to a new location in the same county which is closer to one of the sites and a bit farther than the others. I'm going to try it again with a non SDS scanner. I'm curious if it works from the new location.

 

[yankees6161]

Found one of these on eBay for 40$. Found a thread here about this particular antenna.

 

[prcguy]

That is a very good antenna to cover 800/900MHz and it works ok down to the 760MHz range. It doesn't have tremendous gain, maybe around 3-4dBd but its easily 10dB or more than a typical scanner Discone like the Radio Shack, Diamond D130 or similar in the 700-900MHz range.

$40 is a great price.

Found one of these on eBay for 40$. Found a thread here about this particular antenna.

 

[yankees6161]

I have a Sirio 1300n in the attic. I was looking for gain on the 800mhz. I was thinking yagi until I found the l-com

 

[prcguy]

I think the L-Com will pull in 800MHz signals noticeably better than the Sirio. I also think the ideal wide band setup is a good Discone for 100-512MHz then something like the L-Com for 700-960MHz and combine them with a diplexer.

I have a Sirio 1300n in the attic. I was looking for gain on the 800mhz. I was thinking yagi until I found the l-com

 

[GROL]

I bought one exactly like that one. It does improve signal, but unfortunately it didn't help my application. I was trying to overcome the simulcast issue, but I could not get enough rejection from the other sites as I am so close to all of them. I did get a bit of improvement by mounting it horizontally instead of vertical to reduce overall signal level. It boosted signal to a more usable level for the county over from me, but that one too is simulcast and I still had issues because those sites were mostly all in the same general direction. I finally had to get an SDS100. You would need to convert that connector to BNC or SMA. I would suggest a short pigtail to BNC or SMA. I found a short female N to BNC cable on Amazon for a few dollars. I can make cables, but don't like to especially if the cable is as cheap as the connectors themselves. It looks like it is an N connector like the one I bought. Back when I bought mine there were some cheap higher gain versions that are longer, but I don't see those listed now.

I recently moved to a new location in the same county which is closer to one of the sites and a bit farther than the others. I'm going to try it again with a non SDS scanner. I'm curious if it works from the new location.

So far I am actually getting decent reception from my new location for the simulcast system with that short yagi antenna. More time will confirm it. I did point it towards a distant site on the NC Viper system and had some improvement over the Remtronix antenna I usually keep on my BCD325P2. But not a huge improvement. You will find plans for various versions of yagi antennas online. I have built a few antennas using aluminum tubing, but it tends to get expensive buying aluminum.

 

[GROL]

I think the L-Com will pull in 800MHz signals noticeably better than the Sirio. I also think the ideal wide band setup is a good Discone for 100-512MHz then something like the L-Com for 700-960MHz and combine them with a diplexer.

I think the OP is interested in a directional antenna since he mentioned building a yagi.

 

[vagrant]

Review post #7 and #9. Things changed.

I too have found a discone and an L-Com 800ish omni a good solution using a K&L diplexer. Well, I do use a hand full of filters as well, but that‘s my RFI problem that others may suffer as well.

I think the OP is interested in a directional antenna since he mentioned building a yagi.

 

[GROL]

The most impressive antenna I have found is a Browning BR-137. I use one mobile and tried it on a ground plane mount. It worked well enough on the ground plane that the 17 feet of RG58 cable loss in use was overcome by the antenna gain on 800 Mhz. Gain (dB)136-174 (3db), 380-520(6db), 698-960 (6db)

Some will argue that an omnidirectional antenna cannot have gain. They can over a standard 1/4 wave dipole which is the reference for antennas. The design concentrates the signal so that it is more flat perpendicular to the verticle element instead of waisting energy off the ends of the verticle element. More like a wider donut instead of a ball.

Ultra Multi-Band Antenna 136-174 (VHF), 380-520(UHF), 698-960 MHz 100 Watts

Browning BR-137 Multi-Band Ultra Wide Band Antenna 136-174/380-520/698-960 MHz - Spring Base - 22 in - NMO

theantennafarm.com

TRAM 1465 Land Mobile Base Ground Plane Kit https://a.co/d/heCZCkV

At 800 Mhz, keep in mind feed line losses are going to be enormous without very low loss cable or the use of an antenna amplifier actually mounted at the antenna to overcome feed line loss.
50 feet of RG58 inserts 8.5 db loss.
50 feet of LMR-400 2.1 db loss.

Use the Times Microwave calculator for feed line loss at frequency and length.

Coaxial Cable Attenuation and Power Handling Calculator | Times Microwave Systems

Calculate the attenuation and power handling capability of coaxial cables using the online calculator by Times Microwave Systems. Choose from a variety of cables and get started now!

timesmicrowave.com

I don't even try to use an external antenna at 800 Mhz. I just use the antenna on the radio, and when I use the yagi it sits on a tripod inside at the end of 10 feet of RG59.

The telescopic antenna on my BCD996XT gives the most signal for 700/800 MHz when adjusted to 10 inches. 10 inches is longer than 1/4 wave but apparently balances to near 50 ohms with the case of the scanner being the other half of the dipole.

 

[GROL]

Review post #7 and #9. Things changed.

I too have found a discone and an L-Com 800ish omni a good solution using a K&L diplexer. Well, I do use a hand full of filters as well, but that‘s my RFI problem that others may suffer as well.

Ah! Yes.

 

[prcguy]

The Browning BR-137 is roughly unity gain on VHF, and less than 3dBd gain on UHF and 698-960. They lie about specs to sell antennas. Think about 6dB gain on UHF for example, it takes about 8ft of antenna to reach 6dBd gain on UHF with four stacked dipoles in phase. How is Browning supposed to do that in a 22" long antenna? Answer is they can't.

The most impressive antenna I have found is a Browning BR-137. I use one mobile and tried it on a ground plane mount. It worked well enough on the ground plane that the 17 feet of RG58 cable loss in use was overcome by the antenna gain on 800 Mhz. Gain (dB)136-174 (3db), 380-520(6db), 698-960 (6db)

Some will argue that an omnidirectional antenna cannot have gain. They can over a standard 1/4 wave dipole which is the reference for antennas. The design concentrates the signal so that it is more flat perpendicular to the verticle element instead of waisting energy off the ends of the verticle element. More like a wider donut instead of a ball.

Ultra Multi-Band Antenna 136-174 (VHF), 380-520(UHF), 698-960 MHz 100 Watts

Browning BR-137 Multi-Band Ultra Wide Band Antenna 136-174/380-520/698-960 MHz - Spring Base - 22 in - NMO

theantennafarm.com

TRAM 1465 Land Mobile Base Ground Plane Kit https://a.co/d/heCZCkV

At 800 Mhz, keep in mind feed line losses are going to be enormous without very low loss cable or the use of an antenna amplifier actually mounted at the antenna to overcome feed line loss.
50 feet of RG58 inserts 8.5 db loss.
50 feet of LMR-400 2.1 db loss.

Use the Times Microwave calculator for feed line loss at frequency and length.

Coaxial Cable Attenuation and Power Handling Calculator | Times Microwave Systems

Calculate the attenuation and power handling capability of coaxial cables using the online calculator by Times Microwave Systems. Choose from a variety of cables and get started now!

timesmicrowave.com

I don't even try to use an external antenna at 800 Mhz. I just use the antenna on the radio, and when I use the yagi it sits on a tripod inside at the end of 10 feet of RG59.

The telescopic antenna on my BCD996XT gives the most signal for 700/800 MHz when adjusted to 10 inches. 10 inches is longer than 1/4 wave but apparently balances to near 50 ohms with the case of the scanner being the other half of the dipole.

 

[GROL]

The Browning BR-137 is roughly unity gain on VHF, and less than 3dBd gain on UHF and 698-960. They lie about specs to sell antennas. Think about 6dB gain on UHF for example, it takes about 8ft of antenna to reach 6dBd gain on UHF with four stacked dipoles in phase. How is Browning supposed to do that in a 22" long antenna? Answer is they can't.

Good point. Probably closer to 3dbi and 6dbi. I do know it works very well. I mainly compared it for 700/800 Mhz performance and observed it did very well on VHF, but I have very little that I monitor on 380-520 where I am, in fact practically nothing. Most services of interest here are on 700/800 for State and local, with some VHF for local and Federal.

 

[GROL]

This is probably correct for the BR-137.

Tram Browning BR-137 Multiband Antenna

Buy the best Tram Browning BR-137 Multiband Antenna at Alberta Radio Supply. Shop now!

albertaradiosupply.com

Tram Browning BR-137 Multiband Antenna

136-174 3dBi gain

380-520 6 dBi gain

698-960 6dBi gain

So slightly better than unity gain on VHF and a little more than 3db on 380-520 and 698-960.

Given that feed line losses are very manageable on VHF, unity gain is fine on VHF.

 

[prcguy]

Probably closer to 1.5dBd gain or 3.6dBi on UHF. If you stack two full size 1/2 wavelength dipoles at the proper distance apart and feed them in phase you can get 3dB gain over one dipole. That would be about 4ft tall. If you stack a 1/2 wave whip on top of another 1/2 wave whip with a 1/4 wave phasing coil or 90dge delay in the middle you get about 1.5dB gain. Looking at the antenna construction I would say its 1/2 wave over 1/2 wave on UHF.

This is probably correct for the BR-137.

Tram Browning BR-137 Multiband Antenna

Buy the best Tram Browning BR-137 Multiband Antenna at Alberta Radio Supply. Shop now!

albertaradiosupply.com

Tram Browning BR-137 Multiband Antenna

136-174 3dBi gain

380-520 6 dBi gain

698-960 6dBi gain

So slightly better than unity gain on VHF and a little more than 3db on 380-520 and 698-960.

Given that feed line losses are very manageable on VHF, unity gain is fine on VHF.

 

[GROL]

Probably closer to 1.5dBd gain or 3.6dBi on UHF. If you stack two full size 1/2 wavelength dipoles at the proper distance apart and feed them in phase you can get 3dB gain over one dipole. That would be about 4ft tall. If you stack a 1/2 wave whip on top of another 1/2 wave whip with a 1/4 wave phasing coil or 90dge delay in the middle you get about 1.5dB gain. Looking at the antenna construction I would say its 1/2 wave over 1/2 wave on UHF.

Makes sense. I don't depend on UHF with this antenna, but 1.5 dBd is good considering the size. I use a 2M/70CM mobile antenna for the FT-857D in the car. The Browning is strictly a scanner antenna mainly for 700/800 and a limited degree for VHF where I can receive some local agencies in mountain counties and the Blue Ridge Parkway Rangers. Much of the counties in NC are joining the state owned Viper managed by the Highway Patrol where repeater sites are 700/800.