My $5 436 800Mhz antenna (Easy instructions inside)

[tommypierson]

I see alot of talk about what antenna to use, does this antenna work better than?? ect.

Really simple project that you all should do is make your own "dipole" antenna and it's very easy to make. If you don't want to bother how antennas work here is easy way to make your own dipole antenna and spare the technical part. Just remember that antenna is resonate at a specific frequency. So a 154 Mhz antenna will not be very good at 770 Mhz ect.

With that said he is a very cheap and awesome dipole antenna that I made in 2 minutes.


Buy this: BNC Male to Stackable Binding Posts
1 x BNC Male Plug to Two Dual Banana Binding Female Jack Connector Adapter USA | eBay

And then grab any wire it can be any wire, I used some black stranded 18 guage wire I had laying around and cut it 2 pieces 2 7/8 of an inch and you have a resonant antenna at 750Mhz. And yes we checked it on a Rig Experts 1000.
RigExpert - AA-600/AA-1000/AA-1400 - Antenna Analyzers

You can cut the length of the wire of both sides of the dipole for any frequency you want to get the best reception on that frequency you want to use.

Just make sure each side of the wire is the same length and to determine what length to cut for a specific frequency use this simple dipole calulator.

Just plug in the frequency in the calulator and use the bottom box in the calculator "Quarter Wavelength in Inches" for each side of the dipole.

Hope this helps, especially for people on the simulcast systems as this antenna is amazing on the EBRCS system in the San Francsico east bay area.
Antenna Calculator

 

[kellykeeton]

Why not just buy a $2-$8 antenna off ebay? I mean I am all for learning antenna theory.. But if your going to walk around and such....

 

[tommypierson]

Why not just buy a $2-$8 antenna off ebay? I mean I am all for learning antenna theory.. But if your going to walk around and such....

I walk around all the time, No problem.

And what "Duck" Works better than a Resonant dipole?

 

[safetyobc]

Awesome information. Thanks!

What kind of performance boost do you see compared to a duck?

 

[kellykeeton]

Well for one the directionality of the null point in your antenna makes it less effective in a portable application.. If you feel like debating this feel free to point out any commercial or successful and common used mobile dipole antenna.. Hrm they all use a omni antenna..

And a duck.. Can be a tuned radiating antenna ... Example the radio shack thing .. Or these
http://www.ebay.com/itm/OPTOELECTRO...1000-MHZ-/230211030064?_trksid=p2054897.l4275(I wouldn't recommend buying this just using it as an example graphic of tuned duck antennas, this auction sells one wide 800mhz antenna for $50 you can do much cheaper)



If car mounted this works.. Even works fine for base, you can get these for $5 a pop if you hunt silly sites.
http://www.ebay.com/itm/800-MHz-Mob...pt=US_Radio_Comm_Scanners&hash=item3a8ad8d987


So I would argue along with about a billion application use cases that a "duck" works better in a portable situation..

This contraption that you have made while yes it is home built and for that you should be proud that you did it.. IMO isn't practical in any way for portable use as it's directionality issues, bulkyness, lack of solid connections in a weathered environment, and stress on the sma connector when it gets used in a typical mobile application..

A duck simply terms a flexible antenna - the duck that comes with your scanner OEM is not tuned to 7-800mhz so your performance gains of any tuned antenna (op example included) is going to be "significant" enough that if you dont use an antenna tuned to your use case... It's about damn time you did.

 

[tommypierson]

Awesome information. Thanks!

What kind of performance boost do you see compared to a duck?

Night and day on my local simulcast system. Our control channels are all in the 769-772 Mhz range. This is the system I listen to 90% of time.

 

[tommypierson]

Well for one the directionality of the null point in your antenna makes it less effective in a portable application.. If you feel like debating this feel free to point out any commercial or successful and common used mobile dipole antenna.. Hrm they all use a omni antenna..

And a duck.. Can be a tuned radiating antenna ... Example the radio shack thing .. Or these
Optoelectronics BNC R Duck Antenna RD800 500 1000 MHz | eBay(I wouldn't recommend buying this just using it as an example graphic of tuned duck antennas, this auction sells one wide 800mhz antenna for $50 you can do much cheaper)



If car mounted this works.. Even works fine for base, you can get these for $5 a pop if you hunt silly sites.
800 MHz Mobile Antenna for Motorola Uniden ZK795 | eBay


So I would argue along with about a billion application use cases that a "duck" works better in a portable situation..

This contraption that you have made while yes it is home built and for that you should be proud that you did it.. IMO isn't practical in any way for portable use as it's directionality issues, bulkyness, lack of solid connections in a weathered environment, and stress on the sma connector when it gets used in a typical mobile application..

A duck simply terms a flexible antenna - the duck that comes with your scanner OEM is not tuned to 7-800mhz so your performance gains of any tuned antenna (op example included) is going to be "significant" enough that if you dont use an antenna tuned to your use case... It's about damn time you did.

Ms. Kelly

Thanks for you 2 cents, I will now go and put my head down and throw my contraption away as it is a bad design and idea for that matter.

 

[JamesO]

Polarity is 90 degrees out of phase most of the time, however, there is usually polarity rotation and scatter as well from the transmit antenna in real world applications.

Would be interested to see how the S meter works with the Attenuator on and rotating the radio 90 degrees to get the antenna polarity vertical.

Would be interested to see this in a video as to how much, if any change you will see in doing this.

 

[VE3RADIO]

Ms. Kelly

Thanks for you 2 cents, I will now go and put my head down and throw my contraption away as it is a bad design and idea for that matter.

Its funny how people criticize but do nothing themselves eh? I am glad it made a difference for your enjoyment of the hobby.. sometimes people forget this is a hobby and half the fun is experimenting.. Although I would not walk around with that I would make one for the mobile version I use as a base on my desk.. As for the moron in the peanut gallery.. I have no time for people like that.

 

[tommypierson]

Polarity is 90 degrees out of phase most of the time, however, there is usually polarity rotation and scatter as well from the transmit antenna in real world applications.

Would be interested to see how the S meter works with the Attenuator on and rotating the radio 90 degrees to get the antenna polarity vertical.

Would be interested to see this in a video as to how much, if any change you will see in doing this.

Yes I know 99% of UHF polarity is vertical and my antenna is horizontal. I have tested an 90 degree bnc adapter and yes it does make 2 s units better.

 

[K2KOH]

Kelly, being a ham, I am surprised you weren't complementing tommy for doing what he did...construct something. Too many hams, myself included, depend way too much on commercial products when our hobby originally was based on construction and experimentation. I think tommy did a great job.

 

[LIScanner101]

Yes I know 99% of UHF polarity is vertical and my antenna is horizontal. I have tested an 90 degree bnc adapter and yes it does make 2 s units better.

Tommy, nice job! I was going to comment on the "wrong" polarization of your antenna too, but it's hard to argue with the fact that you seem to have 5 bars in your signal strength meter in your picture.....!!!

 

[kellykeeton]

Kelly, being a ham, I am surprised you weren't complementing tommy for doing what he did...construct something. Too many hams, myself included, depend way too much on commercial products when our hobby originally was based on construction and experimentation. I think tommy did a great job.

you must have ignored where I did.. along with all other other peanuts here. sorry was this what you wanted.."your so awesome, great job, you should work for uniden UPMAN check out this antenna!"

I did I said its great to learn and that he should be proud of his work. however just because you built something, expect criticism, its how you improve and get better.. I dont care for your validation or praise - you built an antenna great.. but its a bad antenna for the use case. fact. you can do better. fact. either take my criticism to improve or whine about it and never learn. whatever...

also the OP said "And what "Duck" Works better than a Resonant dipole?" well.. I explained that to the dismay of some peanuts here.

 

[t_shuffle]

Tommy, thanks for the post. It gave me some ideas.

Kelly, I'll bet you're a lot of fun at parties..:roll:

 

[Forts]

And then grab any wire it can be any wire, I used some black stranded 18 guage wire I had laying around and cut it 2 pieces 2 7/8 of an inch and you have a resonant antenna at 750Mhz.

How did you get 2 7/8 inches? When I plug 750mhz into that calculator it gives me 3.7439 inches?

 

[kellykeeton]

How did you get 2 7/8 inches? When I plug 750mhz into that calculator it gives me 3.7439 inches?

My assumption is the difference from a mathematical calculation of quarterwave vs the OP use of an antenna analyzer - as the antenna analyzer is looking at electrical characteristics vs "wire length math"
typically you would start with the math (234 / design frequency = each dipole side length in feet,
OR - 468 / design frequency = total length in feet.)

then finish up with a SWR meter (which is what the OP implied he did) as mathematically 2 7/8 is somewhere around 1.02ghz (per the photo provided) remember that the antenna wire is only the part that the OP added.. the BNC break out thing also has "wire in it" thus adding that length of "wire" you might have missed out on otherwise. so this antenna is like a "bent L wire antenna" thus making the 3.7 that you expect to see in the photo of linear wire. why a swr meter is handy as it will "clue you into the stuff you forget"

 

[1BMG1]

Night and day on my local simulcast system. Our control channels are all in the 769-772 Mhz range. This is the system I listen to 90% of time.

Good stufff. I am in Danville right near the base of Mt. Diablo. Signal strength is no problem for me because have relays and towers all over the place. Re - Simulcast reception, I still struggle (at times) with Simulcast related garbled transmissions. You think your DIY setup remedies that situation ?

Also - what did you use to make the horizontal antennas ? Kinda looks like mini - ducks : )

 

[kellykeeton]

Simulcast related garbled transmissions. You think your DIY setup remedies that situation ?

a stacked array or true directional antenna is the best bet, however without a improved receiver this is a difficult task. if you are aware of a site that is "just broadcasting the data that you want" then you can attempt to eliminate the multicast issues. if your mobile or portable this will always be an issue for you .. and sometimes for the users of the system with good radios etc..

further reading available on this site on the topic
Simulcast digital distortion - The RadioReference Wiki

 

[flythunderbird]

tommy, great job! One of the things I really like about this hobby is trying out and experimenting with antennas ...