Antenna with most gain?

[G3MiNi]

I am looking to get a new antenna and after reading through these forums there is soooo much to know before making the buy. My question is simply ~ which antenna offers the most dB gain across the full spectrum (30-1300MHz)? (assume best quality coax, short run, grounding ...etc)

 

[N_Jay]

I think an array of 30 meter dishes with liquid nitrogen cooled preamp would take the cake, but I am fairly sure that is not what you meant.

There are no "good" solutions to that band spread. You are best off with a discone if you can fit what you really want to listen to into a 3:1 or 4:1 range.

Other than that the best would be some type of multi-band dipole. Either way you can get between close to 0dBd on the frequencies you are most interested in and avoid the issues that occure with attempting to get gain AND wide bandwidth out of the same antenna.

 

[ledouxfan59]

I think an array of 30 meter dishes with liquid nitrogen cooled preamp would take the cake, but I am fairly sure that is not what you meant.

There are no "good" solutions to that band spread. You are best off with a discone if you can fit what you really want to listen to into a 3:1 or 4:1 range.

Other than that the best would be some type of multi-band dipole. Either way you can get between close to 0dBd on the frequencies you are most interested in and avoid the issues that occure with attempting to get gain AND wide bandwidth out of the same antenna.

ditto , you could also consider yagi's or quads , for the bands you really want

 

[G3MiNi]

Cool ~ thanks for the advice. I've been looking at getting the Diamond D-130J. It sounds like that might be the best approach.

Let me ask about my current antenna. From back in my CB radio days (1970's - lic. KBRF4562) I have an 18 ft. 1/2 wave monopole with three radials (approx 3' each) at the bottom. I'm only slightly educated on antennas, but I am guessing an antenna like this is best for low frequency reception and transmission. I have it connected to my BR330T scanner and I do get decent reception up through the 450MHz frequencies. Above that ~ not so good.

The question: am I correct in assuming this is simply the wrong antenna for my scanner?

 

[blinddog50]

Well looking at the DB you don't have a lot of 800mhz in your area except for the NSR system.
If it works for you, use it.
How old is the antenna?
How old is your coax?(this is important)

 

[G3MiNi]

The antenna is 30 years old (+/-). I clean the point of connection every now and again. The coax is about 5 years old (RG/58). I will upgrading the cable soon to RG6 or 8. The antenna is mounted on the side of the house, right at the ridge line on a 5' mast, placing the radials about 1' above the roof and the tip of the antenna about 19' above the roof. One nice thing is the point of connection to the antenna requires about 10' of wire outside the house ~ so it's a very short run. It's grounded just before entry to the house. I have another 8' or so inside running to my scanner.

 

[bobin]

I think an array of 30 meter dishes with liquid nitrogen cooled preamp would take the cake, but I am fairly sure that is not what you meant.

You guys are funny

 

[N_Jay]

You guys are funny

I try. :lol::lol:

 

[kb2vxa]

One obtains gain at the sacrifice of bandwidth, one obtains bandwidth at the sacrifice of gain. The closest thing to a "full spectrum" antenna is the discone which exhibits a bit less than unity gain or the log periodic beam which exhibits very little gain so the bottom line is your idea of the ideal antenna doesn't exist.

 

[ledouxfan59]

Cool ~ thanks for the advice.
<Snip>

The question: am I correct in assuming this is simply the wrong antenna for my scanner?

not bad , not wrong , but not the greatest either

receiving radios like your scanner , will work regardless of what type of antenna
is connected to them .
transmitting radios , are much more particular , you need to have an antenna
that is "resonant" or you could damage the radio with reflected power
that is what "standing wave ratio" is a measure of .
this is not an issue with receiving radios
however , a cb antenna , will not perform as well at 800 mhz , as say an antenna designed for 800 mhz
as a cb antenna is designed for 27 mhz
there is no "perfect" antenna that will cover every band with gain and bandwidth
a scanner simply covers too much spectrum for that

so if you want gain and bandwidth , then you will have to consider several different antennas

its already been suggested , that you should look at a discone
they don't really exhibit any gain , but they cover the whole spectrum that your scanner
does .
just get it up as high as you can , use a quality coax rated for 800-900 mhz
and forget about it ,
if you want to split hairs , and have the ultimate in gain on every freq . then you will be looking at
a vast array of yagis , quads , Quagis , etc, and a huge bank of rotors to turn each one
the other thing you must consider is that you simply wont be able to receive
anything over your horizon ,(usually about 50 miles on flat land)
on a daily basis
this is simply the nature of digital and fm signals . they are "line of sight"

occasionally though an atmospheric conditon called "Tropospheric Ducting)
occurs and then you could hear police calls from a thousand miles away or better
still though , it wont matter what type of antenna you are using when this occurs

bottom line , your cb antennna will work great for freqs between say 27 and 34 mhz ,
if your using it for receiving , but as you go up in frequency , its resonance falls off
and it becomes less efficient , but will still provide a signal to your scanner

a little long winded , but wanted to make sure you understood that
there is no "perfect" antenna ,
there are trade offs and compromises ,

again , DISCONE !!!!!

Google is your friend


73

 

[eorange]

I've been looking at getting the Diamond D-130J.

This has been my main scanner antenna for years, and it does great on all advertised bands, considering my coax run is about 90 feet. It's a solidly built antenna, too - never had any problems with it. You won't be disappointed.

 

[nycrich]

The antenna with the most gain 30-1300Mhz would be a log periodic. Make sure it is designed for that range. Eg, Create CLP~5130~2N offers 30~1300 MHz bandwidth for transmitting and receiving, with an average forward gain of 10~12 dBi. However it would be directional, unless you use a rotator.

 

[kb2vxa]

The trouble with those gain figures is they are deceptive being estimated at or near the highest frequency. (Sales pitch.) A log periodic exhibits increasing gain with frequency, has nowhere near a linear curve and at the lower frequencies exhibits little to no gain or directionality. In this case having but one or two elements resonant at or near 30MHz any gain or directivity are just about nil on the bottom end.

 

[prcguy]

A Log Periodic has nearly constant gain across its entire frequency range, only a few elements are active at any given frequency. The antenna factor changes with frequency but not the gain.
The Create log mentioned in the next post up is more like 4 to 5dBi gain, and not the 10 or 12dB claimed by the mfr. I compared logs from Create and KMA and ended up buying two KMAs due to the better construction and realistic gain figures.
prcguy

The trouble with those gain figures is they are deceptive being estimated at or near the highest frequency. (Sales pitch.) A log periodic exhibits increasing gain with frequency, has nowhere near a linear curve and at the lower frequencies exhibits little to no gain or directionality. In this case having but one or two elements resonant at or near 30MHz any gain or directivity are just about nil on the bottom end.