Mobile Aviation Antenna for RV

[Don Grillo[_2_]]

I want to purchase an antenna to mount on the top of the ladder on my RV. I've been looking at the RAMI AV-3 and AV-7 antenna's. I will have to fabricate some sort of rotating base so that I can swing the antenna down while traveling as well as to remove the cable. The RAMI AV-3 has a 27" whip and needs to be tuned by cutting to length. The AV-7 is 44" in length and is pre-tuned for freqs 118-137.

Any other cheaper options as these RAMI antenna's are expensive. I will also need a cable extension as they only come with 17'.

Anyone with experience in this area and can provide some guidance?

I will be using this on a hand held Yeasu FTA-450L com radio.

Thanks, Don

P.S. if you are looking for a good handheld that will scan freqs the FTA-450L is great. More features than Icom and much cheaper. On sale with a $25 rebate at Sarasota Avionics till the end of Dec.

http://sarasotaavionics.com/avionics/fta450l

[2G]

On Wednesday, December 6, 2017 at 7:20:30 AM UTC-8, Don Grillo wrote:
> I want to purchase an antenna to mount on the top of the ladder on my RV. I've been looking at the RAMI AV-3 and AV-7 antenna's. I will have to fabricate some sort of rotating base so that I can swing the antenna down while traveling as well as to remove the cable. The RAMI AV-3 has a 27" whip and needs to be tuned by cutting to length. The AV-7 is 44" in length and is pre-tuned for freqs 118-137.
>
> Any other cheaper options as these RAMI antenna's are expensive. I will also need a cable extension as they only come with 17'.
>
> Anyone with experience in this area and can provide some guidance?
>
> I will be using this on a hand held Yeasu FTA-450L com radio.
>
> Thanks, Don
>
> P.S. if you are looking for a good handheld that will scan freqs the FTA-450L is great. More features than Icom and much cheaper. On sale with a $25 rebate at Sarasota Avionics till the end of Dec.
>
> http://sarasotaavionics.com/avionics/fta450l

https://www.amazon.com/gp/offer-listing/B01AIGMVX4/ref=dp_olp_new_mbc?ie=UTF8&condition=new

[Tim Newport-Peace[_4_]]

At 04:29 09 December 2017, 2G wrote:
>On Wednesday, December 6, 2017 at 7:20:30 AM UTC-8, Don Grillo wrote:
>> I want to purchase an antenna to mount on the top of the ladder on my
>RV.=
> I've been looking at the RAMI AV-3 and AV-7 antenna's. I will have to
>fabr=
>icate some sort of rotating base so that I can swing the antenna down
>while=
> traveling as well as to remove the cable. The RAMI AV-3 has a 27" whip
>an=
>d needs to be tuned by cutting to length. The AV-7 is 44" in length and
is
>=
>pre-tuned for freqs 118-137.
>>=20
>> Any other cheaper options as these RAMI antenna's are expensive. I will
>a=
>lso need a cable extension as they only come with 17'.
>>=20
>> Anyone with experience in this area and can provide some guidance?=20
>>=20
>> I will be using this on a hand held Yeasu FTA-450L com radio.=20
>>=20
>> Thanks, Don

>https://www.amazon.com/gp/offer-listing/B01AIGMVX4/ref=3Ddp_olp_new_mbc?ie=
>=3DUTF8&condition=3Dnew
>
The AV-7 is (it says) a 5/8 wave antenna. Taking the mid-band frequency of
127MHz, this equates to a wavelength of 2.24m so 5/8 wavelength is 1.4m,
which is 55 inches. The maximum length of the AV-7 is 44 inches. How does
that work?

For the AV-3, a 1/4 wave antenna, the length would be 22 inches, which is
within the maximum length of the AV-3.

Either a 1/4 wave or 5/8 wave antenna still needs to be a resonant length
for the required frequency for best performance. The only such Airband
antenna that I have ever seen tha did not require tuning was an Array using
rods of different lengths, which is not what the AV-3 or AV-7 are.

Tim Newport-Peace >
http://www.newportpeace.co.uk/icom.htm

[Mike the Strike]

On Saturday, December 9, 2017 at 4:00:10 PM UTC-7, Tim Newport-Peace wrote:
> At 04:29 09 December 2017, 2G wrote:
> >On Wednesday, December 6, 2017 at 7:20:30 AM UTC-8, Don Grillo wrote:
> >> I want to purchase an antenna to mount on the top of the ladder on my
> >RV.=
> > I've been looking at the RAMI AV-3 and AV-7 antenna's. I will have to
> >fabr=
> >icate some sort of rotating base so that I can swing the antenna down
> >while=
> > traveling as well as to remove the cable. The RAMI AV-3 has a 27" whip
> >an=
> >d needs to be tuned by cutting to length. The AV-7 is 44" in length and
> is
> >=
> >pre-tuned for freqs 118-137.
> >>=20
> >> Any other cheaper options as these RAMI antenna's are expensive. I will
> >a=
> >lso need a cable extension as they only come with 17'.
> >>=20
> >> Anyone with experience in this area and can provide some guidance?=20
> >>=20
> >> I will be using this on a hand held Yeasu FTA-450L com radio.=20
> >>=20
> >> Thanks, Don
>
> >https://www.amazon.com/gp/offer-listing/B01AIGMVX4/ref=3Ddp_olp_new_mbc?ie=
> >=3DUTF8&condition=3Dnew
> >
> The AV-7 is (it says) a 5/8 wave antenna. Taking the mid-band frequency of
> 127MHz, this equates to a wavelength of 2.24m so 5/8 wavelength is 1.4m,
> which is 55 inches. The maximum length of the AV-7 is 44 inches. How does
> that work?
>
> For the AV-3, a 1/4 wave antenna, the length would be 22 inches, which is
> within the maximum length of the AV-3.
>
> Either a 1/4 wave or 5/8 wave antenna still needs to be a resonant length
> for the required frequency for best performance. The only such Airband
> antenna that I have ever seen tha did not require tuning was an Array using
> rods of different lengths, which is not what the AV-3 or AV-7 are.
>
> Tim Newport-Peace >
> http://www.newportpeace.co.uk/icom.htm

A 5/8 antenna is typically resonated by adding a base inductor with a tap to match the usual 50-ohm feedline. It's possible to design a nominally 5/8 antenna with a shorter whip and larger inductor, with possibly other matching means to provide a more broadband match.

That's one explanation - another is the specs could be completely made-up!

Mike

[Darryl Ramm]

On Sunday, December 10, 2017 at 8:25:38 AM UTC-8, Mike the Strike wrote:
> On Saturday, December 9, 2017 at 4:00:10 PM UTC-7, Tim Newport-Peace wrote:
> > At 04:29 09 December 2017, 2G wrote:
> > >On Wednesday, December 6, 2017 at 7:20:30 AM UTC-8, Don Grillo wrote:
> > >> I want to purchase an antenna to mount on the top of the ladder on my
> > >RV.=
> > > I've been looking at the RAMI AV-3 and AV-7 antenna's. I will have to
> > >fabr=
> > >icate some sort of rotating base so that I can swing the antenna down
> > >while=
> > > traveling as well as to remove the cable. The RAMI AV-3 has a 27" whip
> > >an=
> > >d needs to be tuned by cutting to length. The AV-7 is 44" in length and
> > is
> > >=
> > >pre-tuned for freqs 118-137.
> > >>=20
> > >> Any other cheaper options as these RAMI antenna's are expensive. I will
> > >a=
> > >lso need a cable extension as they only come with 17'.
> > >>=20
> > >> Anyone with experience in this area and can provide some guidance?=20
> > >>=20
> > >> I will be using this on a hand held Yeasu FTA-450L com radio.=20
> > >>=20
> > >> Thanks, Don
> >
> > >https://www.amazon.com/gp/offer-listing/B01AIGMVX4/ref=3Ddp_olp_new_mbc?ie=
> > >=3DUTF8&condition=3Dnew
> > >
> > The AV-7 is (it says) a 5/8 wave antenna. Taking the mid-band frequency of
> > 127MHz, this equates to a wavelength of 2.24m so 5/8 wavelength is 1.4m,
> > which is 55 inches. The maximum length of the AV-7 is 44 inches. How does
> > that work?
> >
> > For the AV-3, a 1/4 wave antenna, the length would be 22 inches, which is
> > within the maximum length of the AV-3.
> >
> > Either a 1/4 wave or 5/8 wave antenna still needs to be a resonant length
> > for the required frequency for best performance. The only such Airband
> > antenna that I have ever seen tha did not require tuning was an Array using
> > rods of different lengths, which is not what the AV-3 or AV-7 are.
> >
> > Tim Newport-Peace >
> > http://www.newportpeace.co.uk/icom.htm
>
> A 5/8 antenna is typically resonated by adding a base inductor with a tap to match the usual 50-ohm feedline. It's possible to design a nominally 5/8 antenna with a shorter whip and larger inductor, with possibly other matching means to provide a more broadband match.
>
> That's one explanation - another is the specs could be completely made-up!
>
> Mike

And you get less than the free space 5/8 wavelength due to real-world effects, antenna end effects and physical diameter. That correction is usually less than a 10% shortening. In this case the antennas seem to be made to magnetic mount on a car or other vehicle and i wonder if they assume that and are tuned to correct for that ground plane effect. Yep 5/8 antennas don't need a ground plane, but having one close by changes the tuning.

[[email protected]]

yes amazing! using a cheap radio shack SWR meter and "tuning" a 1/4, 5/8 or evan a full wave antennae, makes such a big improvement in the reception and transmit functions that my motorhome 1/4 wave magnetic mount with a 18 gauge 18"x18" ground plane siliconed to the roof is getting me 100 mile reception and transmit functions on a terra 720tx radio.

[2G]

On Sunday, December 10, 2017 at 5:09:56 PM UTC-8, wrote:
> yes amazing! using a cheap radio shack SWR meter and "tuning" a 1/4, 5/8 or evan a full wave antennae, makes such a big improvement in the reception and transmit functions that my motorhome 1/4 wave magnetic mount with a 18 gauge 18"x18" ground plane siliconed to the roof is getting me 100 mile reception and transmit functions on a terra 720tx radio.

Here is some good info on how to construct a ground plane:

http://www.ai4ji.com/Projects/antennas/groundplanes.htm