Lately I've been using this little "high gain" antenna that my company
uses in poor reception areas to boost the signal strength of these
little cellular data transmitters we use in our business.

It's about a foot tall with a little coily section, and a magnetic
base. Probably your typical antenna for 800 Mhz.. works great.


A couple of days ago, I bought a Scantenna and I mounted it up on a
homemade mast. Here's a directory of pics I took while building it
all:

http://www.faradic.net/~sphynx/antenna

My little omni-directional 800 Mhz antenna is near the top of my roof
(not in the pictures).

The antenna you see in the pictures is probably 6ft below the highest
peak of my roof. I used every bit of the 50ft. of RG6U coax that came
with the Scantenna and only have the F-to-BNC adapter in-line.

With the Scantenna, the lower band reception seems to be much improved
over the smaller antenna I had been using before, but the reception is
the 800 - 900 Mhz range seems to be a little worse.

Now, I know that the case may be that the little specialty antenna I
have (made special for +3dB gain in 800Mhz or whatever) will always
out-perform the Scantenna, but I was just curious if this is indeed
the case.

Are there any improvements I can make in my design? I was thinking of
elevating it another 6ft or so, but I'm forced to wonder if that would
really be of any significant benefit.

Reception on most other bands seems crystal clear, and I've never seen
my scanner's S-meter register so many darned bars!

Any ideas would be appreciated. Thanks!

En Tempest va escriure en Mon, 27 Sep 2004 04:12:17 GMT:

Lately I've been using this little "high gain" antenna that my company
uses in poor reception areas to boost the signal strength of these
little cellular data transmitters we use in our business.
....
A couple of days ago, I bought a Scantenna and I mounted it up on a
homemade mast. Here's a directory of pics I took while building it
all:

http://www.faradic.net/~sphynx/antenna

My little omni-directional 800 Mhz antenna is near the top of my roof
(not in the pictures).

The antenna you see in the pictures is probably 6ft below the highest
peak of my roof. I used every bit of the 50ft. of RG6U coax that came
with the Scantenna and only have the F-to-BNC adapter in-line.

With the Scantenna, the lower band reception seems to be much improved
over the smaller antenna I had been using before, but the reception is
the 800 - 900 Mhz range seems to be a little worse.
....
Are there any improvements I can make in my design? I was thinking of
elevating it another 6ft or so, but I'm forced to wonder if that would
really be of any significant benefit.
....
Any ideas would be appreciated. Thanks!

Hi,

If you are using 50 ft of cable from antenna to receiver try
replacing the antenna provided cable with other 75 ohm coax of
lower loss at 800 MHz. Use only good-brand cable with known
characteristics, don't rely on your local radio shop selling a
cable of unknown origin. Also use the right connectors of good
quality, without adapters. This should not be very expensive to
try.

If your cable is already very-good (which I doubt) you will get
about equal. If your cable is not so good (likely) you can easily
gain several dBs (at 800MHz that is, below 300~400 MHz there
won't be much of a difference).

--
Toni

"Auto" = prefijo griego que significa "no funciona"

On Mon, 27 Sep 2004 10:20:54 +0200, Toni
wrote:

En Tempest va escriure en Mon, 27 Sep 2004 04:12:17 GMT:

Lately I've been using this little "high gain" antenna that my company
uses in poor reception areas to boost the signal strength of these
little cellular data transmitters we use in our business.
...
A couple of days ago, I bought a Scantenna and I mounted it up on a
homemade mast. Here's a directory of pics I took while building it
all:

http://www.faradic.net/~sphynx/antenna

My little omni-directional 800 Mhz antenna is near the top of my roof
(not in the pictures).

The antenna you see in the pictures is probably 6ft below the highest
peak of my roof. I used every bit of the 50ft. of RG6U coax that came
with the Scantenna and only have the F-to-BNC adapter in-line.

With the Scantenna, the lower band reception seems to be much improved
over the smaller antenna I had been using before, but the reception is
the 800 - 900 Mhz range seems to be a little worse.
...
Are there any improvements I can make in my design? I was thinking of
elevating it another 6ft or so, but I'm forced to wonder if that would
really be of any significant benefit.
...
Any ideas would be appreciated. Thanks!

Hi,

If you are using 50 ft of cable from antenna to receiver try
replacing the antenna provided cable with other 75 ohm coax of
lower loss at 800 MHz. Use only good-brand cable with known
characteristics, don't rely on your local radio shop selling a
cable of unknown origin. Also use the right connectors of good
quality, without adapters. This should not be very expensive to
try.

If your cable is already very-good (which I doubt) you will get
about equal. If your cable is not so good (likely) you can easily
gain several dBs (at 800MHz that is, below 300~400 MHz there
won't be much of a difference).


Thanks for the help, Toni.

I'm using the 50ft of RG-6U coax sent with the Scantenna. It has
F-conectors on each end, and the kit came with an F-to-BNC adapter.

What would you suggest specifically for cabling? I'm pretty new to
this.

Also, based on the pictures I posted, should I elevate the antenna
more? Typically how much of a benefit would I get out of maybe 6ft
more height?

Thanks

"Tempest" wrote in message
...
Thanks for the help, Toni.

I'm using the 50ft of RG-6U coax sent with the Scantenna. It has
F-conectors on each end, and the kit came with an F-to-BNC adapter.

What would you suggest specifically for cabling? I'm pretty new to
this.

Also, based on the pictures I posted, should I elevate the antenna
more? Typically how much of a benefit would I get out of maybe 6ft
more height?

Thanks

Although people will tell you that you have to use 50 ohm cable for
communications type equipment (including scanners), the reality is that few
of us will notice the difference it makes. Having said that, I have kept
all of my comms tye equipment feedlines on 50 ohm cabling. In a home base
type setup, I run a minimum of RG213, and if playing on the higher freqs, I
use better, typically Belden 9913 or hardline heliax. These types of cables
are typically rather expensive unless you can get it secondhand which can
reduce the costs quite significantly (which is what I do - always on the
lookout for cheap cable even if I don't need it at the time of purchase).
It is up to you whether you want to spend the extra money on the lower loss
cables, but it is not always worth it for the average user.
As to height - well height is might, particularly as the frequencies get
higher, but depending on the type of cable used, the benefits of the extra
height can be negated by the cable loss involved in getting the antenna
higher. For my scanner I try and get the antenna at about 10 metres above
ground (around 33 feet in height), the benefit of additional height will not
always be apparent particularly if you are listening mainly to local
repeater based services, but if you are listening to simplex stations or
more distant repeaters you will notice a difference. If you cannot get it
much higher, at least get it clear of surrounding structures and it should
provide improved performance, particularly with services that you may be
listening to that are currently obscured by your house.





Matt

I'm using the 50ft of RG-6U coax sent with the Scantenna. It has
F-conectors on each end, and the kit came with an F-to-BNC adapter.

What would you suggest specifically for cabling? I'm pretty new to
this.

Also, based on the pictures I posted, should I elevate the antenna
more? Typically how much of a benefit would I get out of maybe 6ft
more height?

Thanks

Although people will tell you that you have to use 50 ohm cable for
communications type equipment (including scanners), the reality is that few
of us will notice the difference it makes. Having said that, I have kept
all of my comms tye equipment feedlines on 50 ohm cabling. In a home base
type setup, I run a minimum of RG213, and if playing on the higher freqs, I
use better, typically Belden 9913 or hardline heliax. These types of cables
are typically rather expensive unless you can get it secondhand which can
reduce the costs quite significantly (which is what I do - always on the
lookout for cheap cable even if I don't need it at the time of purchase).
It is up to you whether you want to spend the extra money on the lower loss
cables, but it is not always worth it for the average user.
As to height - well height is might, particularly as the frequencies get
higher, but depending on the type of cable used, the benefits of the extra
height can be negated by the cable loss involved in getting the antenna
higher. For my scanner I try and get the antenna at about 10 metres above
ground (around 33 feet in height), the benefit of additional height will not
always be apparent particularly if you are listening mainly to local
repeater based services, but if you are listening to simplex stations or
more distant repeaters you will notice a difference. If you cannot get it
much higher, at least get it clear of surrounding structures and it should
provide improved performance, particularly with services that you may be
listening to that are currently obscured by your house.

Hi Tempest,

I basically agree with Matt:

50 or 75 ohms will make small difference. The real difference is
in using good quality low-loss cable. One possible source of
reference is http://thewireman.com/ but there are many others.
You don't necessarily want "the best cable around", just look at
the dB /100 ft loss figure for 800 MHz (or close) and find the
loss for your 50 ft. 1 or 2 dB difference between cables won't
make much difference for casual listening. 3 or more dB begins to
reduce a lot your reception. If you buy the cable and conectors
at a real store they should be able to solder the connectors for
you. Mind you, even if this seems simple it is a difficult job to
do properly the first time, and a badly installed connector may
ruin all your gains.

As for antenna height, the said is good: For normal conditions
you want the minimum height that clears the antenna from all
surrounding obstacles. From your photos it seems that the antenna
is too low. A bit more height, just enough to get it above the
roof top, will probably improve reception in that direction.

--
Toni

"Auto" = prefijo griego que significa "no funciona"

Matt Although people will tell you that you have to use 50 ohm cable
Matt for communications type equipment (including scanners), the
Matt reality is that few of us will notice the difference it makes.

When later one graduates to ham radio, both transmitting and
receiving, one will be glad one chose 50 ohm cable.

"Dan Jacobson" wrote in message
...
Matt Although people will tell you that you have to use 50 ohm cable
Matt for communications type equipment (including scanners), the
Matt reality is that few of us will notice the difference it makes.

When later one graduates to ham radio, both transmitting and
receiving, one will be glad one chose 50 ohm cable.

I am also an amateur radio operator and have been for quite a few years now.
I personally use 50 ohm cable for all of my installs, BUT, for the average
user, they will not notice the difference on receive only runs - sorry
should have made it clearer that it was for receive only use.




Matt