Re: Marine Radio using Aviation Antennae

[Wayne Paul]

Doug,

Most aircraft antenna's are 1/4 wave length (about 22 inches.) A quarter
wavelength on marine frequencies is approximately 17 and a half inches.
This is out of the range of most handheld matching circuits. My conclusion
is that the answer to your question is no.

Wayne
http://www.soaridaho.com/Schreder


"Doug" > wrote in message
...
> I want to get a handheld marine radio for my amphib Husky. I wouild like
to
> plug it in to my aviation outside antennae that I have installed for my
> aviation handheld. Will this work? Marine frequencies are
> a.. TX 156.025-157.425 MHz
> b.. RX 156.025-163.275 MHz
> (from the Icom web site).
>
>

[Buff5200]

You could try the Ham radio market. What you are looking for is an
Antenna Tuner
for the 70cm band. What you want is an antenna tuner that can capactively
"shorten" the 22" aircraft antenna and cause it to match the frequencies
that would
normally use a 17" antenna. You might want to look at www.aesham.com.

Wayne Paul wrote:

>Doug,
>
>Most aircraft antenna's are 1/4 wave length (about 22 inches.) A quarter
>wavelength on marine frequencies is approximately 17 and a half inches.
>This is out of the range of most handheld matching circuits. My conclusion
>is that the answer to your question is no.
>
>Wayne
>http://www.soaridaho.com/Schreder
>
>
>"Doug" > wrote in message
...
>
>
>>I want to get a handheld marine radio for my amphib Husky. I wouild like
>>
>>
>to
>
>
>>plug it in to my aviation outside antennae that I have installed for my
>>aviation handheld. Will this work? Marine frequencies are
>> a.. TX 156.025-157.425 MHz
>> b.. RX 156.025-163.275 MHz
>>(from the Icom web site).
>>
>>
>>
>>
>
>
>
>

[Tim Ward]

"Buff5200" > wrote in message
...
> You could try the Ham radio market. What you are looking for is an
> Antenna Tuner
> for the 70cm band. What you want is an antenna tuner that can capactively
> "shorten" the 22" aircraft antenna and cause it to match the frequencies
> that would
> normally use a 17" antenna. You might want to look at www.aesham.com.

No. The 70 cm amateur band is around 440 MHz -- way above 160 MHz.
The marine frequencies would be closest to 2 meters, and not all that close.

I think a dedicated antenna is going to be simpler, cheaper, and work
better.

Jim, I believe at one time you posted a pointer to an advisory circular of
best practices for installing non-aviation band radios in aircraft. Maybe
you could dig that out again.

Tim Ward

[Buff5200]

Tim Ward wrote:

>
>
>No. The 70 cm amateur band is around 440 MHz -- way above 160 MHz.
>The marine frequencies would be closest to 2 meters, and not all that close.
>
>I think a dedicated antenna is going to be simpler, cheaper, and work
>better.
>
>

Sorry, my misprint, I meant a dual band 2M/70cm tuner.

Absolutely, a dedicated antenna is the best move. Unless you are trying
to mount an extra antenna
on a certified aircraft. Lots of paperwork and $$$. I was speaking to
the concept of using a HT marine
radio on an antenna "normally" used for aviation band, and already
installed in the airframe.

>
>
>
>

[Tim Ward]

"Buff5200" > wrote in message
...
>
>
> Tim Ward wrote:
>
> >
> >
> >No. The 70 cm amateur band is around 440 MHz -- way above 160 MHz.
> >The marine frequencies would be closest to 2 meters, and not all that
close.
> >
> >I think a dedicated antenna is going to be simpler, cheaper, and work
> >better.
> >
> >
>
> Sorry, my misprint, I meant a dual band 2M/70cm tuner.

I understood you to mean an antenna tuner.


> Absolutely, a dedicated antenna is the best move. Unless you are trying
> to mount an extra antenna
> on a certified aircraft. Lots of paperwork and $$$. I was speaking to
> the concept of using a HT marine
> radio on an antenna "normally" used for aviation band, and already
> installed in the airframe.

That's why I mentioned Jim Weir's previous posting of a pointer to an AC
about mounting non-aviation radios in airplanes. I think last time it was
in connection with amateur radio in an airplane, but the principals would be
the same.
Tim Ward

[Ken Mattsson]

While on the subject of antennas, having built a couple of Jim´s plumber
delights, could this antenna design in principle be used for any bands or
can it only be built for center frequencies within the VHF-band? You see, I
have this little cute Yaesu scanner and I´d love to build a few more
antennas for it, base antennas that is. I already have a set of homemade
portable antennas for it out of bnc connectors with welding rod sticks.

Cheers, Ken
Finland

[Craig Davidson]

Ken Mattsson wrote in message ...
>While on the subject of antennas, having built a couple of Jim´s plumber
>delights, could this antenna design in principle be used for any bands or
>can it only be built for center frequencies within the VHF-band? >
>Cheers, Ken
>Finland
>

Every antenna I have seen can be built to any frequency. Do it by adjusting
the dimensions of the antenna inversely proportional to the frequency. for
example if you want the antenna to work at twice the frequency then the
dimensions should be half. Likewise if you want to use the antenna at half
the frequency then the dimensions should be doubled.

[Jim Weir]

That is true...to a crude first approximation. The thickness of the antenna as
a function of frequency and antenna length is not so linear. The actual
calculation goes:

Calculate the THEORETICAL length as a submultiple of the wavelength.
Then do the finagle fatness factor for element thickness.

Jim


"Craig Davidson" >
shared these priceless pearls of wisdom:

->
->Ken Mattsson wrote in message ...
->>While on the subject of antennas, having built a couple of Jim´s plumber
->>delights, could this antenna design in principle be used for any bands or
->>can it only be built for center frequencies within the VHF-band? >
->>Cheers, Ken
->>Finland
->>
->
->Every antenna I have seen can be built to any frequency. Do it by adjusting
->the dimensions of the antenna inversely proportional to the frequency. for
->example if you want the antenna to work at twice the frequency then the
->dimensions should be half. Likewise if you want to use the antenna at half
->the frequency then the dimensions should be doubled.
->

Jim Weir (A&P/IA, CFI, & other good alphabet soup)
VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
http://www.rst-engr.com

[Steve Roberts]

find a ham radio operator in your area with a VHF capable SWR meter
(or just order a 2 meter swr meter from AES) if the SWR (standing
wave ratio) is greater then 2:1 then the antenna is not well enough
matched for even casual use. A good match is from say 1.1:1 to 1.40:1.
SWR meter hooks between the radio and the antenna and measures
transmitted and reflected power (well , sort of, the real explanation
would take a couple of pages). If the antenna isnt a good transmitter
at a particular frequency, then its a good reflector of RF back down
the cable. That RF has to go somewhere and that somewhere is back
into the final stage of the transmitter, causing heat and maybe
burnout.
Most modern marine HTs are designed with a circuit that backs off the
TX power or shuts down the transmitter if tyou have a bad match.

If this is for use at altitude in a non safety of life application, IE
calling your wife on the boat, you can get away with a crappy swr.
However keep in mind that if you transmit from any reasonable
altitude, your range is increased dramtically, and the marine RADIO is
FM, not AM, and the strongest singal wins on FM, unlike AM whjere they
overlap, so using a a decent marine radio at 5000 feet above San Fran,
you could end up capturing the channel down the whole west coast.
Probably somewhat illegal unless your doing some form of air to ground
work as part of your flying.

if your just gonna receive, the airband antenna will be just fine.

Steve Roberts , N8VKD

[Jim Weir]

Horsefeathers. A 2:1 VSWR transmits 90% of the applied power. A 3:1 VSWR
transmits 75% of the applied power. Have you actually ever MEASURED a
commercial aircraft band antenna from bandedge to bandedge as installed on an
aircraft?

Jim


(Steve Roberts)
shared these priceless pearls of wisdom:

->find a ham radio operator in your area with a VHF capable SWR meter
->(or just order a 2 meter swr meter from AES) if the SWR (standing
->wave ratio) is greater then 2:1 then the antenna is not well enough
->matched for even casual use.
Jim Weir (A&P/IA, CFI, & other good alphabet soup)
VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
http://www.rst-engr.com

[[email protected]]

As I'm sure you know, and to be fair to the previous poster, you are
implying 90% of full power for 2:1 VSWR. As he stated any decent
transmitter has VSWR protection so it will back off the power to
protect itself. You will then only transmitt 90% of what the
transmitter is now putting out!

Do you know what transmitter output power would you realistically
expect in these conditions?

Personally I have accept 3:1 VSWR for occasional use as long as the PA
is protected. One time on holiday I lost one half of my 14MHz inverted
V dipole but still manage to reach UK from Southern Spain with 10W
SSB. Don't even ask what the VSWR meter was reading, it looked like it
was all being reflected!

On Mon, 11 Aug 2003 07:45:34 -0700, Jim Weir > wrote:

>Horsefeathers. A 2:1 VSWR transmits 90% of the applied power. A 3:1 VSWR
>transmits 75% of the applied power. Have you actually ever MEASURED a
>commercial aircraft band antenna from bandedge to bandedge as installed on an
>aircraft?
>
>Jim
>
>
(Steve Roberts)
>shared these priceless pearls of wisdom:
>
>->find a ham radio operator in your area with a VHF capable SWR meter
>->(or just order a 2 meter swr meter from AES) if the SWR (standing
>->wave ratio) is greater then 2:1 then the antenna is not well enough
>->matched for even casual use.
>Jim Weir (A&P/IA, CFI, & other good alphabet soup)
>VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
>http://www.rst-engr.com



E-mail (Remove Space after pilot): pilot

[Thomas Pappano]

Ken Mattsson wrote:
>> if your just gonna receive, the airband antenna will be just fine.
>>
>> Steve Roberts , N8VKD
>
>
> Steve,
>
> I was just thinking of using it with the scanner, no transmitting, on the
> ground and not from the air.
>
> But back to the basic question. Can this J-stick design by Jim be used for
> any bands, that is be built for any specific wavelength, or is the J-stick
> design for some reason good only for the VHF-range? You see, it would be fun
> to build a couple of these antennas on other wavelengths just to explore
> what can be heard. A set of base antennas for snooping around on the
> different bands. Now that I have found out where to get parts for this water
> pipe antenna, it would be relatively easy to make a few more, if only the
> desing allows for it.
>
> Best regards, Ken
>
>
Yes, it will. Just use the formula to make the elements the
proper lengths for your frequencies of interest. The J is a classic
and will work for most any band. You may need to use guy wires
if you descend into the HF bands, however. 8-)

Tom Pappano, PP-ASEL-IA

[Jim Weir]

Not to mention the filing with the FAA for airspace intrusion {;-)

Jim


Thomas Pappano >
shared these priceless pearls of wisdom:

You may need to use guy wires
->if you descend into the HF bands, however. 8-)
->
->Tom Pappano, PP-ASEL-IA

Jim Weir (A&P/IA, CFI, & other good alphabet soup)
VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
http://www.rst-engr.com