All my RX path questions

[prcguy]

Are some yagi better on sides and on the back then others if so what should I look for

Generally speaking most commercial Yagis of the same gain should have similar 3dB beamwidth, side lobes and F/B ratio. When they design for very narrow band width like amateur CW/SSB the gain, side lobes and F/B can be improved but for wider band antennas you give up some of that to make it play over a wider frequency range.

A problem with the antenna industry is some companies lie and make up gain numbers, so you really have to know who you are dealing with.

 

[Bonkk083]

Generally speaking most commercial Yagis of the same gain should have similar 3dB beamwidth, side lobes and F/B ratio. When they design for very narrow band width like amateur CW/SSB the gain, side lobes and F/B can be improved but for wider band antennas you give up some of that to make it play over a wider frequency range.

A problem with the antenna industry is some companies lie and make up gain numbers, so you really have to know who you are dealing with.

If a yagi and omni had the same gain would they work the same

 

[krokus]

Last question hopefully, Which antenna would have the best chance of reaching 36-45 miles but my terrain is a little hilly, I have info from a los tool I can upload if needed

Terrawave T09150Y11206T Yagi Base Antenna | Scanner Master

Terrawave T09150Y11206T Yagi Base Antenna

www.scannermaster.com

Pardon Our Interruption...

If you only care about that one direction, the Terrawave will maximize your signal in one direction.

 

[ka3aaa]

they are two different animals, the yagi is directional, the omni is not.

 

[buddrousa]

@bonkkSome of the best advice for you would start studying Ham Radio and meet with your local Ham Radio Club and learn all you can about RF.

 

[Bonkk083]

they are two different animals, the yagi is directional, the omni is no

That's not what I meant will it pickup the same if they had the same amount of gain between a omni and yagi, just say 11 dbi omni is 360 and a yagi is one direction so the yagi be stronger regardless

 

[prcguy]

they are two different animals, the yagi is directional, the omni is not.

I’ve compared a lot of stuff at the same location going from a 10dB Yagi to a 10dB omni and they can have very different results. Some signals I know that are not line of sight can sometimes come in better on the Yagi and sometimes better on the omni.

A Yagi is like a point source where a stacked colinear or dipole array has a much larger pickup area and it depends on if the multipath is out of phase and destructive or in phase and additive. The larger pickup area can multiply the effects. Some local signals can come in better on a Yagi and I believe due to multipath reflections off huge metal bridges or tank farms between the source and my antenna and the Yagi can reduce some of the off path reflections.

The only way to know the answers to most of these questions is to get one of everything discussed and try it. Thats not the cheapest way to the end but it will leave you with the best solution and some priceless knowledge.

 

[Bonkk083]

I’ve compared a lot of stuff at the same location going from a 10dB Yagi to a 10dB omni and they can have very different results. Some signals I know that are not line of sight can sometimes come in better on the Yagi and sometimes better on the omni.

A Yagi is like a point source where a stacked colinear or dipole array has a much larger pickup area and it depends on if the multipath is out of phase and destructive or in phase and additive. The larger pickup area can multiply the effects. Some local signals can come in better on a Yagi and I believe due to multipath reflections off huge metal bridges or tank farms between the source and my antenna and the Yagi can reduce some of the off path reflections.

The only way to know the answers to most of these questions is to get one of everything discussed and try it. Thats not the cheapest way to the end but it will leave you with the best solution and some priceless knowledge.

What is a non line of sight antenna

 

[prcguy]

What is a non line of sight antenna

Something over a hill or blocked by obstructions.

 

[Bonkk083]

Can you get a amp for 800 mhz

 

[dave3825]

Yes, called an LNA (Low Noise Amplifier). Generally they are wide banded. I have been using a 12 dollar one from ebay. I will be getting either one of these or a PGA-103+ based one soon.

Nooelec - Nooelec LaNA - Wideband Ultra Low-Noise Amplifier (LNA) Module w/ Enclosure & Accessories. 20MHz-4GHz Capability w/ Bias-Tee, USB & DC Power Options

<p>LaNA is a very high performance, wideband LNA module designed for general purpose SDR applications. <p>Each module allows for 3 different power options, <b>but you should only power with one option at any given time!</b> The recommended power input

www.nooelec.com

New Products in Our Store: Wideband LNA + Spare V3 Metal Enclosures

We've just released two new products in our store. The first is a low cost general purpose wideband LNA and the second is some spare RTL-SDR V3 aluminum enclosures. The wideband LNA is currently available for shipping from our Chinese warehouse and will be available on Amazon in a few days time...

www.rtl-sdr.com

 

[buddrousa]

9 times out of 10 an amp makes things worse not better.

 

[Bonkk083]

9 times out of 10 an amp makes things worse not better.

I was thinking of getting a low gain 800mhz antenna and a amp to boost the signal like a high gain antenna

 

[mmckenna]

I was thinking of getting a low gain 800mhz antenna and a amp to boost the signal like a high gain antenna

Amplifiers amplify everything in their designed band. That might include cellular. Low gain antenna + amp is probably not a good idea as cellular signals can easily overwhelm your scanner and end up decreasing performance considerably. Really careful filtering can help, but that all gets expensive. Usually using the right antenna for the application is the way to go.

 

[KevinC]

I was thinking of getting a low gain 800mhz antenna and a amp to boost the signal like a high gain antenna

In the commercial world amplifiers are usually used to overcome a loss somewhere in the RX path (coax, multi-coupler, etc..) and typically provide minimal additional gain (and if they do it has to be managed). I'd work on a better, higher antenna (but height is your friend so work on that first).

 

[Bonkk083]

In the commercial world amplifiers are usually used to overcome a loss somewhere in the RX path (coax, multi-coupler, etc..) and typically provide minimal additional gain (and if they do it has to be managed). I'd work on a better, higher antenna (but height is your friend so work on that first).

Will 4 dbi make much of a difference, it's regarding 11 dbi antenna vs a 15 dbi antenna

 

[KevinC]

Will 4 dbi make much of a difference, it's regarding 11 dbi antenna vs a 15 dbi antenna

Pretty sure the gain questions were addressed in your other thread.

 

[prcguy]

Will 4 dbi make much of a difference, it's regarding 11 dbi antenna vs a 15 dbi antenna

Yes. 3dB difference in an antenna is 2X the signal level, 4dB is 2.51X. This is assuming the antenna gains are real and not lies made up by the antenna company.

 

[Bonkk083]

Yes. 3dB difference in an antenna is 2X the signal level, 4dB is 2.51X. This is assuming the antenna gains are real and not lies made up by the antenna company.

They are 2 towers one to the northwest that's 37 miles and another tower to the northeast that's 30 miles the omni is 11 dbi and the yagi 15 dbi since it makes a difference I might just have to choose one direction

 

[dave3825]

I was thinking of getting a low gain 800mhz antenna and a amp to boost the signal like a high gain antenna

Why not just get a high gain 800 antenna? I use an lna but run it on a lower voltage to gain a slight boost on an 800 yagi. Full voltage makes the noise floor pretty high and pretty useless.