Antenna question

[Cressida81]

So, i've got a pro-95 and was having some reception problems, so i ditched the rubber antenna that came with it and bought a R-Shack antenna (i think its like 10in). Its the kind that expands and contracts and has a black plastic thing in the middle. After reading the instructions i realized that since it reccomends extending the antenna to a certain length based on the frequency i want to hear that it ends of being about as long as the one i ditched. So my question is, Did i actually get a better antenna by doing this? Should i only have the antenna extended 6.22in as the calculations show i should. Or should i fully extend the antenna?

umm... yeah, help?

 

[dangitdoug]

Depends on what you want to listen to. I have a recently purchased Pro95 and have been very happy with the stock antenna. Your reception issues may have more to do with location than the antenna. I have a telescoping antenna that I have used occasionally on my handheld scanners, with no noticeable improvement in reception. The telescoping does work with my handheld CB's, but I honestly could not tell you the last time I used those.

I also have a Pro92 and BC235XLT. The reception on my Pro95 is the best of the three.

 

[rpowley]

dangitdoug is right - it depends on what you are listening to. I have 3 antenna's for my 95's - The stock, telescoping center load, and 800MHz. I use the telescoping for air and other VHF and the 800 for UHF. I normally use the stock when in my car driving around locally

 

[MacombMonitor]

There is no "one does all" antenna for scanners. The rubber duck that ships with most scanners is proof of that, as that is what they tried to do. Instead of being a great antenna at any frequency, it's a poor antenna at all frequencies!

However, the one you just bought is an attempt at overcoming that obstacle. The fact that it telescopes, makes it tunable by the user, so you can optimize it for a particular band. If you wanted to monitor railroad in the 160MHz band, you could adjust that antenna to be optimized for that band. Same for any other band. It becomes a problem when you scan frequencies in several bands, as you would look like a trombone player on crack, trying to keep it adjusted fast enough to keep up with the scanner!

What we all end up doing, if we're serious about the hobby, is having multiple antennas that we change depending on the situation.

What bands are you having problems receiving well?

Bill

 

[Cressida81]

What i've been listening to is the 480's Los Angeles Sheriff's Dept. The reception is sporadic, the same freq i listen to at one point will sometimes be almost perfect and then the next day or hour will be bad again.
Also, sometimes i hear the dispatcher really well, loud and clear, and other times i only hear the hiss of background radio noise with a really faint dispatcher voice. i'd like to have consistant results because the static drives my roommates nuts. Also, i'm trying to do this on a very slim budget, as in, no budget (i felt lame buying a $14 center balanced antenna).

Radio shack had a mountable "scanner" antenna for something like $40, I could put that right outside my window on the roof and see if that helps. Would it help? Would taking the handheld up to the roof and seeing if it gets better reception up there be a good test to see if it will help?

 

[mix-man]

Well I dont know if this will help you or not, but when I used to live in town I had my scanner setup as a base unit, I strecthed a long piece of speaker wire out the window (20 foot), It worked pretty well beleave it or not... As I said though I dont know if it will help in your case or not, but its was free seeing how I have tons of speaker wire laying around I dont know too much about antennas... I bought a mag mount "all band" radio shack antenna and IMHO it sucks bad, only thing I can find for my truck though.

Edit: I mostly monitor 155's and 800's our town uses those freqs most often.

73's and good luck
KE5HLR

 

[ka3jjz]

Many ham radio shops - and places such as HRO - sell a Larsen 150/400/800 Mhz mobile scanner antenna that is supposed to be very good. Another good choice - and I don't believe I'm saying this, since the coax this unit utilizes has a good deal of loss at 800 - is the Valor PMM3B. Cheap, but it seems to be effective. I haven't used either of these antennas - I have an Austin Spectra which I use with my 245 which works pretty well, but it is pricey- but both have been written about extensively on the antennas forum.
You can find LOTS of scanner antenna links on the Scanner Antenna wiki page on this site. Just click on the blue text, and you'll be taken there.

 

[ka3jjz]

What i've been listening to is the 480's Los Angeles Sheriff's Dept. The reception is sporadic, the same freq i listen to at one point will sometimes be almost perfect and then the next day or hour will be bad again.
Also, sometimes i hear the dispatcher really well, loud and clear, and other times i only hear the hiss of background radio noise with a really faint dispatcher voice. i'd like to have consistant results because the static drives my roommates nuts. Also, i'm trying to do this on a very slim budget, as in, no budget (i felt lame buying a $14 center balanced antenna).

Radio shack had a mountable "scanner" antenna for something like $40, I could put that right outside my window on the roof and see if that helps. Would it help? Would taking the handheld up to the roof and seeing if it gets better reception up there be a good test to see if it will help?

It sounds very much like you are experiencing the effects of other objects, hills, buildings and so forth partially blocking the signal you want to hear. This is quite common; the higher you go in frequency, the more this effect can be noticed.

Getting up high is indeed the answer; I would imagine things would improve if you were to get up to the roof. However, height and size increases have a downside; you may start to receive so much signal, that the radio is overloaded. When this happens, one of two things can occur; you might start hearing pagers and other junk in places you didn't before, or the scanner will start to hear less This is because it's being swamped with so many signals, it will try to lock onto one signal among the bandpass, and reduce the sensitivity on all the others. This is a very broad description of 'desense'.

Our scanner antennas wiki (as mentioned in the previous post) has several possibilities; however, if you're just using the scanner in one spot, why not build a quick ground plane antenna for the 480 mhz band? Putting that on the roof, and feeding it with the right coax, will make a world of difference.

There are a few rubber duck antennas on the wiki as well; the Diamond RH77CA is one that has been mentioned in the antennas forum before. It might help to jump on over to the California state forum, and see what others are using that have PRO95s in the LA area. That's often the best way to find out what works best; what works in one area may not do very well in another. 73s Mike

 

[jagr707]

I have the RS centerloaded antenna also. Mine was about $14 also. I find it works pretty good most of the time depending on what I am doing. Since I mostly scan 800 and VHF, it is only 2 adjustments. I found for ~800 mhz just extend the bottom half one space. For VHF extend most of it. It deally does help with VHF and mil air reception but is about the same as the duck for 800-900. I dont listen to much UHF but havent noticed any problems with it.



J

 

[SIMON11]

The best scanner antenna I own for reception is the RS telescopic super-gainer. It is about 105cm long fully extended. It picks up superb right down to the low frequencies.
Bulky but magnificent!

 

[Cressida81]

I was just reading in another thread about using tv antenna amps for boost the reception of my scanner. Would that work for my case with the 480Mhz range? if so how would i actually install it to work with my center balanced Rshack antenna?

 

[Cressida81]

i stopped by the Radio shack today to see if they had anything. And i found this antenna for $19 http://www.radioshack.com/product/i...032075.2032078.2032098&pg=2&parentPage=family
its the Outdoor VHF-Hi/UHF Scanner Antenna. it was $5 cheaper than the list price.

Anyways, i have all i need to mount it but i have questions about the cable run. It takes a certain type of adaptor that i'm not familiar with. I already have a coaxial cable running from the roof to my room, it would be really great if i could use that cable run instead of finding a new one. So what/where can i find the adaptors that i need for that?
I am open to buying the new cable, but i don't want to make the hole in my wall any bigger (its just big enough for the TV coax cable i already have running).

 

[amusement]

I used a indoor TV FM/AM antenna for my scanner. It worked well around buildings and trees (100-160mhz, 800mhz).

It had two flat panels (unable to locate image) that could be positioned. It had 32dB built in amp. This worked well for those far away 150mhz range train transmissions.

I don't like using "rabbit ears". Signal attenuation was too great in the 800mhz range. The "flat plane" or "panel" worked for me and my urban area.

 

[RISC777]

i stopped by the Radio shack today to see if they had anything. And i found this antenna for $19 http://www.radioshack.com/product/index.jsp?productId=2103641&cp=2032052.2032075.2032078.2032098&pg=2&parentPage=family
its the Outdoor VHF-Hi/UHF Scanner Antenna. it was $5 cheaper than the list price.

Anyways, i have all i need to mount it but i have questions about the cable run. It takes a certain type of adaptor that i'm not familiar with. I already have a coaxial cable running from the roof to my room, it would be really great if i could use that cable run instead of finding a new one. So what/where can i find the adaptors that i need for that?
I am open to buying the new cable, but i don't want to make the hole in my wall any bigger (its just big enough for the TV coax cable i already have running).

PL-259 at the antenna end (to go to its SO-239). BNC-male at the scanner end. I'm taking it for granted that you have a scanner with a BNC (female) connection.

 

[SIMON11]

I was just reading in another thread about using tv antenna amps for boost the reception of my scanner. Would that work for my case with the 480Mhz range? if so how would i actually install it to work with my center balanced Rshack antenna?

I use a tv amp quite successfully. It is marked aerial and tv out. I just use coax plugs on the leads in and out.

 

[Cressida81]

Problems solved! Radio Shack small ground plane antenna mounted on the Chimney has made my reception SO much better now!

 

[RISC777]

Uhf

It's interesting to me, Cressidea81, that have experienced such variation in reception quality. (So long as I'm taking it correctly when you wrote "480s" to mean a UHF system.) There's a UHF system I monitor that is consistent, no perceptible variation in quality on multiple models of scanners. While at the same time I do experience similar to you the problems in reception of a VHF system. Atmospherics and signal bounce, etc. kill me with that one. Glad you found a pretty simple solution to your situation, though!

 

[hotdjdave]

To answer the question more specifically, YES, the length of the antenna does matter. The length of the antenna is proportional to the frequency being used (transmitted or received); hence, the designations 6M, 2M, 70cm, etc. These are the full length of the antenna for the frequency in that range (band). However, usually, a size different than the full wave length is used, i.e. half wave or quarter wave, because it would be impractical to use an antenna at its full length. The antenna is cut down in a ½, ¼, 5/8 or other size to shorten the length for mobile use. Most base antennas use the full length because it is much easier to mount a larger antenna on a mast.

However, the size of the antenna is not as important when receiving, as opposed to extremely important when transmitting. The key is to get an antenna close to the size to match the frequency you are trying to monitor, whether full wave or fractional wave. As mentioned, some antennas incorporate the ability to receive (and even transmit) on multiple bands. The lower the frequency, the longer the antenna; the higher the frequency, the shorter the antenna. Theoretically, you would want an exact match (antenna size to frequency match) for each band to which you are listening. Professional radios have specifically tuned antennas to match the freqeuncy it uses.

I remember when I was a kid, I used to stick a hanger in the back of my black and white TV to get a reception because the telescoping antenna was broken – and no, I am not that old, it is just what my parents could afford to get me; I felt privileged to have my own TV in my room.

The black plastic thing in the middle, called a coil (or center coil if it is on the center of the antenna or base coil if it is on the base of the antenna) is actually wound up wire to make it so you do not have to have a, say, 2 meter (6 foot) long antenna, but a much shorter antenna with much of the length wound up in the coil. Some antennas have more than one coil.

If you actually took apart many rubber ducky antennas, the wire inside would be wound up like a spring; the wire is much longer than the length of the rubber or plastic shell. That is why most VHF radios have a somewhat short FAT antenna, the antenna is actually much longer, but wound up inside the plastic/rubber shell; and a UHF is much thinner and slightly longer to the look, but in reality, much shorter. It is a matter of practicality and aesthetics.

 

[RISC777]

hotdjdave .......
quick question(s).
If it is incorporated into antenna design, coils and winds, why have I seen it stated not to wind or coil cable from an antenna to a receiver/scanner? And it piques my curiousity that an RF wave (I picture a wave-form seen on an oscilliscope screen) being 2 meters in "height" ... if/when a receive antenna designed to receive the same is coiled, it's then not physically 2 meters in physical or measurable height/length ... how does that "work" ?

 

[kb2vxa]

Hi Cress and all,

My my, how the replies have strayed from your question! Having that particular antenna lying in a drawer because it has the Motorola plug and my present scanner has a BNC jack I'll draw on my previous experience with it. (;->)

That coil is a series load that comes into play only on VHF Lo Band so when listening to that band fully extend the whip. Since it isolates the upper portion on higher bands and the lower portion is a fixed 12" it's a rather poor compromise there. The bottom line is it's a rather iffy antenna overall, I don't particularly recomend it since there are much better ones available.

Pardon me, I can't resist having some fun with this flash-back to my CB days.
Dave "Radio Check"
I've got mine.
"Read You Loud and Clear"
I can read but of you I'm not so sure.

Then there is that moronic question "What's your 10-20?"
Between 10-19 and 10-21. (Actually I can't be more than a few miles from YOUR 20 you dope!)

There's more and it only gets worse so I'll quit while I'm a head. (No, the spelling is correct.)

Back to seriosity;
"If it is incorporated into antenna design, coils and winds, why have I seen it stated not to wind or coil cable from an antenna to a receiver/scanner?"

Risc, I have no idea where you picked up that misinformation, coiling coaxial transmission line has no effect on it's charateristics.

"And it piques my curiousity that an RF wave (I picture a wave-form seen on an oscilliscope screen) being 2 meters in "height" ..."
HUH? I have never seen a silly-scope screen two meters in height, that would be one HUGE scope. Now if you picture it (in your mind) as being two meters in length (crest to crest) you have it right.

"...if/when a receive antenna designed to receive the same is coiled, it's then not physically 2 meters in physical or measurable height/length ... how does that "work" ?"
Simply stated, it doesn't work. There's a lot to be said about wavelength, inductance, capacitance, phase angles and delay, resonance, etc., far too much to go into here and give you a course in antenna theory. I suggest you take a course at an electronics school or at least read up on it, you're way off the beam and about to land in the marsh outside the airport. I say this in hopes your question doesn't open that dreaded can of worms, volumes of misinformation that'll lead you farther astray when you can get a proper education from those engineers who wrote the books.