Just wanting to cheaply/quickly/easily boost the pulling power of my tuner. Are those cheap RF amplifiers much use to boost RF reception any good?
Also, anyone know of a useful link for a DIY FM antenna and other ways to optimise reception ? (I'm not keen to modify the circuitry inside my tuner - the tuner's good, just the location is in a RF hole.
Cheers.
Also, anyone know of a useful link for a DIY FM antenna and other ways to optimise reception ? (I'm not keen to modify the circuitry inside my tuner - the tuner's good, just the location is in a RF hole.
Cheers.
A booster or antenna amplifier only helps if it has lower noise figure than the input stage in your radio. No booster beats a good antenna.
I found a link that looks good:
http://radio.meteor.free.fr/us/yagi_fm.html
I found a link that looks good:
http://radio.meteor.free.fr/us/yagi_fm.html
Jax is correct when the booster amp is fitted at near the tuner.
If the booster is fitted at the mast-head (next to the antenna), there will be an improvement. This is because the loss of the downlead is subtracted from the noise. There is also sometimes an improvement in VSWR (matching).
At 100MHz 'ish the improvement will only be significant if the downlead is poor quality or very long.
You have got a roof antenna....
?
If the booster is fitted at the mast-head (next to the antenna), there will be an improvement. This is because the loss of the downlead is subtracted from the noise. There is also sometimes an improvement in VSWR (matching).
At 100MHz 'ish the improvement will only be significant if the downlead is poor quality or very long.
You have got a roof antenna....
?I've always been under the impression that an amplifier cannot
help a good good tuner except for exceptionally bad reception
conditions and a very good antenna is still needed, and a mast
head amplifier is the way to do it.
Or the device guaranteed to make other FM enthusiasts
green with envy, the remote mast head rotator.
My one book dealing with antenna's mentions circular polarisation,
and has a design for a freestanding vertical end fed half wave
antenna, its the most ergonomic indoor design I've seen.
(Basically a base with two 1/2" round vertical
sections, one 7.5ft long the other 2.5ft long)
What antenna are you using at the moment ?
sreten.
help a good good tuner except for exceptionally bad reception
conditions and a very good antenna is still needed, and a mast
head amplifier is the way to do it.
Or the device guaranteed to make other FM enthusiasts
green with envy, the remote mast head rotator.
My one book dealing with antenna's mentions circular polarisation,
and has a design for a freestanding vertical end fed half wave
antenna, its the most ergonomic indoor design I've seen.
(Basically a base with two 1/2" round vertical
sections, one 7.5ft long the other 2.5ft long)
What antenna are you using at the moment ?
sreten.
Here's a link to an easy to make FM antenna. I want to try this sometime but have not had the time.
http://zbconline.com/antenna.html
http://zbconline.com/antenna.html
Imrpving FM Reception
Hi, the best booster is a multi-element antenna. The more elements the better. In the UK is a firm advertising in a UK Hifi journal that has a nice one. Sorry don't recall the names.
Use double shielded coax cable from antenna to receiver, as short as posssible in length to minimise losses.
Hi, the best booster is a multi-element antenna. The more elements the better. In the UK is a firm advertising in a UK Hifi journal that has a nice one. Sorry don't recall the names.
Use double shielded coax cable from antenna to receiver, as short as posssible in length to minimise losses.
Hi,
Thanks for your input everyone who posted a reply. Much appreciated and exactly the info I was after. I think I'll have a go at building the antenna from the link that Scott Wurcer posted. Looks simple and cheap.
I'll post another reply to let you know how well it works once I've got around to building it.
Thanks for your input everyone who posted a reply. Much appreciated and exactly the info I was after. I think I'll have a go at building the antenna from the link that Scott Wurcer posted. Looks simple and cheap.
I'll post another reply to let you know how well it works once I've got around to building it.
hello,
I have had excellent results with J-pole antenna's.
check out the following sites.
http://latham.dropbear.id.au/antenna/
http://www.mycal.net/old/projects/mpr/jpole.htm
the following site contains an excellent optimization program for your favorite radio frequency.
http://www.sedan.org/jpol.htm
and some pictures to see how a commercial application is done.
http://users.cis.net/kingpop/J-pole-pix.htm
Id go out to the roof to take a picture of the one I made, but it's raining in L.A. right now!
good luck
carl
I have had excellent results with J-pole antenna's.
check out the following sites.
http://latham.dropbear.id.au/antenna/
http://www.mycal.net/old/projects/mpr/jpole.htm
the following site contains an excellent optimization program for your favorite radio frequency.
http://www.sedan.org/jpol.htm
and some pictures to see how a commercial application is done.
http://users.cis.net/kingpop/J-pole-pix.htm
Id go out to the roof to take a picture of the one I made, but it's raining in L.A. right now!
good luck
carl
I've just built and installed a jpole as per one of the
examples, with a coax feed. My ham radio neighbor loaned
me his swr analyzer so I may be able to see if it's even
remotely tuned correctly for the FM band. I cut the elements
a little long so I'll have some room for tweaking.
I'm hoping the bandwidth is reasonably wide; I used 1/2"
copper tubing (gave me some practice soldering copper
tubing, too), though I might consider 3/4" on the next one.
Relatively easy project, and the results seem good for local
reception on the stations I wanted. Lots of multipath in
my location and a few stations seem to suffer as a result
with this presumably omnidirectional antenna, but thankfully
not the ones I wanted.
My first RF project in many years! Photos may eventually
follow (I wanna digital camera but can't afford a Canon Rebel)
--Damon
examples, with a coax feed. My ham radio neighbor loaned
me his swr analyzer so I may be able to see if it's even
remotely tuned correctly for the FM band. I cut the elements
a little long so I'll have some room for tweaking.
I'm hoping the bandwidth is reasonably wide; I used 1/2"
copper tubing (gave me some practice soldering copper
tubing, too), though I might consider 3/4" on the next one.
Relatively easy project, and the results seem good for local
reception on the stations I wanted. Lots of multipath in
my location and a few stations seem to suffer as a result
with this presumably omnidirectional antenna, but thankfully
not the ones I wanted.
My first RF project in many years! Photos may eventually
follow (I wanna digital camera but can't afford a Canon Rebel)
--Damon
My jpole measured 1:1 at 88MHz and 2:1 at 92MHz at 50 ohm impedance; that's reasonable bandwidth. I may trim it to the middle of the band and try another one with 3/4" tubing to see if the bandwidth can be increased.
I've done this project 'by the book' so far and don't
understand how the antenna actually works; it should be possible
to tune it for a 75 ohm impedance though for receiving purposes
this isn't critical. The actual impedance reading was more around
40 ohms, but I'm not familiar how this instrument (MFJ Enterprises,
MFJ-249) works so I may have misinterpreted something. One meter
reads SWR, the other reads impedance and the subject is a bit
complex.
As much as I'd like to have a big log periodic on a rotator, this
is a more practical answer for now. Ben Franklin would accuse me
of making a lightning rod, and I did make sure it was well-grounded.
It's a rugged and simple design, and I recommend it if you can't
get a directional antenna installed. I also ran across a modification that will turn a jpole into a kind of Yagi vertical
antenna that has some front-to-back ratio.
No serious attempts to DX, hoping to pull in a Portland station or
two. The reception is solid on the three local stations I like:
KWJZ (smooth jazz), KING (classical), and KPLU (traditional jazz and blues, NPR) Alas, no one in the region carries Hearts of Space...
Need to replace the burnt-out lamps on my tuner display so I can
read it!
I've done this project 'by the book' so far and don't
understand how the antenna actually works; it should be possible
to tune it for a 75 ohm impedance though for receiving purposes
this isn't critical. The actual impedance reading was more around
40 ohms, but I'm not familiar how this instrument (MFJ Enterprises,
MFJ-249) works so I may have misinterpreted something. One meter
reads SWR, the other reads impedance and the subject is a bit
complex.
As much as I'd like to have a big log periodic on a rotator, this
is a more practical answer for now. Ben Franklin would accuse me
of making a lightning rod, and I did make sure it was well-grounded.
It's a rugged and simple design, and I recommend it if you can't
get a directional antenna installed. I also ran across a modification that will turn a jpole into a kind of Yagi vertical
antenna that has some front-to-back ratio.
No serious attempts to DX, hoping to pull in a Portland station or
two. The reception is solid on the three local stations I like:
KWJZ (smooth jazz), KING (classical), and KPLU (traditional jazz and blues, NPR) Alas, no one in the region carries Hearts of Space...
Need to replace the burnt-out lamps on my tuner display so I can
read it!
Elso,
Are you thinking of the Ron Smith Galaxie range? They are excellent but very large.
http://members.fortunecity.com/g7nnt/products/galaxie.html
For good FM in most places you want a good, high-gain directional antenna to help eliminate multipath, which is a killer for sonic performance.
There are large benefits to be had from having excessive gain in the antenna (almost always better than a booster amp, with their potential noise and overload problems), good high-quality low-loss feeders (use double-screened satellite-grade coax) and then attenuators at the tuner end to bring the signal into the correct order for the tuner. You want the signal level to meet the full quieting sensitivity of the tuner you use.
The advantages of this approach are the attenuator improves matching, provides some isolation and attenuates the multipath pick up from the cable itself.
Andy.
Andy:
In my many years of playing with outdoor FM antennas,
those Rod Smith Galaxies are the most outrageous I've ever seen.
I want one. Badly.
At one time I had a JFET preselector and a switched RF
attenuator which helped my mediocre Heathkit AJ-29 plow
through local signal overload. Since I moved to Seattle,
I haven't had much opportunity or money to play that
game. For the present, this Jpole will have to do.
--Damon, who once had a stack pair of JFD's biggest log periodics
and still has a useable Finco FM-4G. Both companies are
long gone.
In my many years of playing with outdoor FM antennas,
those Rod Smith Galaxies are the most outrageous I've ever seen.
I want one. Badly.
At one time I had a JFET preselector and a switched RF
attenuator which helped my mediocre Heathkit AJ-29 plow
through local signal overload. Since I moved to Seattle,
I haven't had much opportunity or money to play that
game. For the present, this Jpole will have to do.
--Damon, who once had a stack pair of JFD's biggest log periodics
and still has a useable Finco FM-4G. Both companies are
long gone.
Just to clear up a few matters for non RF inclined readers....
The J-pole and Slim Jim are vertically polarized , and more important- horizontal omni directional antennas,......... doing very good for omni directional reception.....
For weak signal reception you need a good directional antenna, like a yagi. Drawback is of course that it is directional,... and may need a rotor if you want reception in more than one direction.
A good quality masthead amplifier will do well for all types of receiving antennas.
Polarization of FM broadcast used to be horisontal, and are thus more compatible to the traditional yagi FM antenna. Receiving with opposite polarization gives what is known as "polarization loss", reducing the signal.
Qiute strange it is, though , this modern fashion of tugging home a receiver and expecting good reception without any form of antenna!
QRT de LA5**
The J-pole and Slim Jim are vertically polarized , and more important- horizontal omni directional antennas,......... doing very good for omni directional reception.....
For weak signal reception you need a good directional antenna, like a yagi. Drawback is of course that it is directional,... and may need a rotor if you want reception in more than one direction.
A good quality masthead amplifier will do well for all types of receiving antennas.
Polarization of FM broadcast used to be horisontal, and are thus more compatible to the traditional yagi FM antenna. Receiving with opposite polarization gives what is known as "polarization loss", reducing the signal.
Qiute strange it is, though , this modern fashion of tugging home a receiver and expecting good reception without any form of antenna!
QRT de LA5**
Agreed on all but one
This is the only area I'd disagree with you on. There's no substitute (in terms of noise figure / ultimate performance) for a higher gain antenna.
Whilst there may be good masthead amps out there, most that people are likely to come across aimed at this market are noisy and exhibit poor overload / intercept performance.
In our increasingly noisy RF environment, I'd only use a masthead where absolutely necessary.
Andy.
This is the only area I'd disagree with you on. There's no substitute (in terms of noise figure / ultimate performance) for a higher gain antenna.
Whilst there may be good masthead amps out there, most that people are likely to come across aimed at this market are noisy and exhibit poor overload / intercept performance.
In our increasingly noisy RF environment, I'd only use a masthead where absolutely necessary.
Andy.
Concerning the masthead amp, - I won't disagree either!
One problem though is that most modern receivers seems to be designed for living next door to the transmitter,- most of them have rather poor sensitivity. This can be remedied by a high quality masthead amp, - but again I agree with you, - most masthead amps of today are of a rather poor quality, - and the good ones are likely to be expensive, if you can find them.
Indeed, - if the tradeoff is between a larger antenna or small antenna/amplifier, the larger antenna is the the bettter way., but even with a large antenna, a masthead amp can be a good compensation for long cable runs.
Another problem, maybe not so common, is wind load on laarger antennas. In my neighbourhood, large antennas have a very short lifetime, unless being exceptionally rigid mechanically.
( I do occasionally get wind gust at 70 knots + .......... )
One problem though is that most modern receivers seems to be designed for living next door to the transmitter,- most of them have rather poor sensitivity. This can be remedied by a high quality masthead amp, - but again I agree with you, - most masthead amps of today are of a rather poor quality, - and the good ones are likely to be expensive, if you can find them.
Indeed, - if the tradeoff is between a larger antenna or small antenna/amplifier, the larger antenna is the the bettter way., but even with a large antenna, a masthead amp can be a good compensation for long cable runs.
Another problem, maybe not so common, is wind load on laarger antennas. In my neighbourhood, large antennas have a very short lifetime, unless being exceptionally rigid mechanically.
( I do occasionally get wind gust at 70 knots + ..........
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