Tuning a Rainco antenna

[Eric Greenwell[_4_]]

I have a Rainco ground station antenna I bought from Graham Thompson
about a millennium ago. The construction is 2' of 1" diameter aluminum
tube at the bottom with a 4' whip on top. The coax attaches at the base.

My problem is it's VSWR at 123.3 is 2.5; at 118.1 it's only 1.5. I'm
assuming it's too long, but maybe there are coils or such inside that do
the adjustment. Does anyone know how to tune this antenna?

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)
- "Transponders in Sailplanes - Feb/2010" also ADS-B, PCAS, Flarm
http://tinyurl.com/yb3xywl

[ray conlon]

On Jul 19, 5:37*pm, Eric Greenwell > wrote:
> I have a Rainco ground station antenna I bought from Graham Thompson
> about a millennium ago. The construction is 2' of 1" diameter aluminum
> tube at the bottom with a 4' whip on top. The coax attaches at the base.
>
> My problem is it's VSWR at 123.3 is 2.5; at 118.1 it's only 1.5. I'm
> assuming it's too long, but maybe there are coils or such inside that do
> the adjustment. Does anyone know how to tune this antenna?
>
> --
> Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
> email me)
> - "Transponders in Sailplanes - Feb/2010" also ADS-B, PCAS, Flarmhttp://tinyurl.com/yb3xywl

VHF antennas are tuned by adjusting the length of the radiator
element, usually the vertical one, lower freq the longer the element,
the higher the freq the shorter...

[Eric Greenwell[_4_]]

On 7/19/2011 7:26 PM, ray conlon wrote:
> On Jul 19, 5:37 pm, Eric > wrote:
>> I have a Rainco ground station antenna I bought from Graham Thompson
>> about a millennium ago. The construction is 2' of 1" diameter aluminum
>> tube at the bottom with a 4' whip on top. The coax attaches at the base.
>>
>> My problem is it's VSWR at 123.3 is 2.5; at 118.1 it's only 1.5. I'm
>> assuming it's too long, but maybe there are coils or such inside that do
>> the adjustment. Does anyone know how to tune this antenna?
>>
>> --
>> Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
>> email me)
>> - "Transponders in Sailplanes - Feb/2010" also ADS-B, PCAS, Flarmhttp://tinyurl.com/yb3xywl
>
> VHF antennas are tuned by adjusting the length of the radiator
> element, usually the vertical one, lower freq the longer the element,
> the higher the freq the shorter...

I'm hoping there is some way to adjust the Rainco antenna without
cutting off pieces of the whip, which has a nice ball formed on the end.

I used to have the instructions, but I can't find them in my records any
more.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)
- "Transponders in Sailplanes - Feb/2010" also ADS-B, PCAS, Flarm
http://tinyurl.com/yb3xywl
- "A Guide to Self-launching Sailplane Operation Mar/2004" Much of what
you need to know tinyurl.com/yfs7tnz

[Paul Remde]

Hi Eric,

For the Larsen antennas I sell, there is also a ball at the end of the whip,
so I cut-off the other end of the whip. But I'm sure you thought of that
already.

I documented the tools I used to tune the antennas on my web page here:
http://www.cumulus-soaring.com/larsen.htm

Best Regards,

Paul Remde
Cumulus Soaring, Inc.

"Eric Greenwell" > wrote in message
...
> On 7/19/2011 7:26 PM, ray conlon wrote:
>> On Jul 19, 5:37 pm, Eric > wrote:
>>> I have a Rainco ground station antenna I bought from Graham Thompson
>>> about a millennium ago. The construction is 2' of 1" diameter aluminum
>>> tube at the bottom with a 4' whip on top. The coax attaches at the base.
>>>
>>> My problem is it's VSWR at 123.3 is 2.5; at 118.1 it's only 1.5. I'm
>>> assuming it's too long, but maybe there are coils or such inside that do
>>> the adjustment. Does anyone know how to tune this antenna?
>>>
>>> --
>>> Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
>>> email me)
>>> - "Transponders in Sailplanes - Feb/2010" also ADS-B, PCAS,
>>> Flarmhttp://tinyurl.com/yb3xywl
>>
>> VHF antennas are tuned by adjusting the length of the radiator
>> element, usually the vertical one, lower freq the longer the element,
>> the higher the freq the shorter...
>
> I'm hoping there is some way to adjust the Rainco antenna without cutting
> off pieces of the whip, which has a nice ball formed on the end.
>
> I used to have the instructions, but I can't find them in my records any
> more.
>
> --
> Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email
> me)
> - "Transponders in Sailplanes - Feb/2010" also ADS-B, PCAS, Flarm
> http://tinyurl.com/yb3xywl
> - "A Guide to Self-launching Sailplane Operation Mar/2004" Much of what
> you need to know tinyurl.com/yfs7tnz

[Andy[_1_]]

On Jul 19, 9:31*pm, Eric Greenwell > wrote:

> I'm hoping there is some way to adjust the Rainco antenna without
> cutting off pieces of the whip, which has a nice ball formed on the end.
>

I'm sure that if you open it up there will be a way to adjust the
length without cutting the tip off. I thought I had the same antenna
as you but my sleeve is larger diameter. My measurements are:

sleeve dia 1.25 inch
sleeve length 26.2 inch (insulator to base excluding mounting bolt)
exposed whip length 44.7 inch

Don't know the resonant freq or the SWR at 123.3 but I may have to
measure it now you brought the subject up.

It appears the antenna can be opened by removing a single screw that
attaches the mounting base to the sleeve. The insulated cap at the
top of the sleeve is retained by staking (center punched indent).

I have a vague recollection that these antennas originated in AZ and
were designed by Ryan. Quite a few club members were using them a
while ago. I did a search of some ham radio antenna deign sources but
didn't find exactly the same design. Sleeve monopole is the best
generic description I could find.

If you open it up let me know what you find, and/or send pictures.

Andy

[Eric Greenwell[_4_]]

On 7/20/2011 5:43 AM, Andy wrote:
> On Jul 19, 9:31 pm, Eric > wrote:
>
>> I'm hoping there is some way to adjust the Rainco antenna without
>> cutting off pieces of the whip, which has a nice ball formed on the end.
>>
>
> I'm sure that if you open it up there will be a way to adjust the
> length without cutting the tip off. I thought I had the same antenna
> as you but my sleeve is larger diameter. My measurements are:
>
> sleeve dia 1.25 inch
> sleeve length 26.2 inch (insulator to base excluding mounting bolt)
> exposed whip length 44.7 inch
>
> Don't know the resonant freq or the SWR at 123.3 but I may have to
> measure it now you brought the subject up.
>
> It appears the antenna can be opened by removing a single screw that
> attaches the mounting base to the sleeve. The insulated cap at the
> top of the sleeve is retained by staking (center punched indent).
>
> I have a vague recollection that these antennas originated in AZ and
> were designed by Ryan. Quite a few club members were using them a
> while ago. I did a search of some ham radio antenna deign sources but
> didn't find exactly the same design. Sleeve monopole is the best
> generic description I could find.
>
> If you open it up let me know what you find, and/or send pictures.

Your measurements are exactly what mine measures, so I think we do have
the same antenna. It's the motorhome's antenna, so I'll wait until after
our upcoming trip before trying to open it up. Don't want to fix
something that's working well just before I need it!

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)

- "A Guide to Self-launching Sailplane Operation Mar/2004" Much of what
you need to know tinyurl.com/yfs7tnz

[Free Flight 107]

I was about to make one of those types of antennas years ago, but a
Ham friend took me tothe local Ham shop and the guy at the counter put
together the right parts for a 5/8th wave antenna with a magnetic base
for about $80.
Works great, I receive gliders when those with 1/4 wave antennas don't
even hear them. It's about 5 ft high and removable which is a geat
advantage over the bolted to the bumper kind. SWR at 123.4 came in at
1.1 or less with 125.0 only 1.2 or so. It seems to combine the best of
all worlds in sensitivity, range of freqs and handling.

Give it a try,

Wayne

[Andy[_1_]]

On Jul 20, 2:24*pm, Free Flight 107 > wrote:
> I was about to make one of those types of antennas years ago, but a
> Ham friend took me tothe local Ham shop and the guy at the counter put
> together the right parts for a 5/8th wave antenna with a magnetic base
> for about $80.
> Works great, I receive gliders when those with 1/4 wave antennas don't
> even hear them. It's about 5 ft high and removable which is a geat
> advantage over the bolted to the bumper kind. SWR at 123.4 came in at
> 1.1 or less with 125.0 only 1.2 or so. It seems to combine the best of
> all worlds in sensitivity, range of freqs and handling.
>
> Give it a try,
>
> Wayne

I used a 5/8 base loaded magnetic mount for years and still have it.
These antennas (antennae) work very well on steel roof vehicles,
particularly if they are tuned for a specific spot on the roof and
always mounted in the same place. They have higher gain that a 1/4
wave but, just as importantly, a lower radiation angle.

They don't stick well on glass top vans or on glass motor homes
though. To use one there you'd need a ground plane and a steel mount
plate.

Andy