I am thinking about upgrading my radio transceiver in my 40 year old Pegasus. By this time, I wouldn't be surprised if the coax cable to the fin antenna has degraded due to cracked insulation or something like that. Any suggestions about replacing the antenna and cable? Or should I just go with a dipole inside the (fiberglass) tail boom? I will test the system with an SWR meter and hope I don't have any issues, but just in case.....

Hi Mark,

Don't forget that the antenna needs to be mounted (near) vertically to
match the polarization of all the other transmitters and receivers out
there.

Dan
5J

On 9/6/23 06:53, Mark628CA wrote:
> I am thinking about upgrading my radio transceiver in my 40 year old Pegasus. By this time, I wouldn't be surprised if the coax cable to the fin antenna has degraded due to cracked insulation or something like that. Any suggestions about replacing the antenna and cable? Or should I just go with a dipole inside the (fiberglass) tail boom? I will test the system with an SWR meter and hope I don't have any issues, but just in case.....

Your antenna and cable are probably in good shape. You may want to change the BNC connector if too rusty.
To change antenna and cables, you will have to dig holes in the glider.

You can check your stuff using a common SRW meter. But your new radio will certainly tell you if your antenna is bad

> You can check your stuff using a common SRW meter. But your new radio will certainly tell you if your antenna is bad

I will be checking the cable and antenna with an SWR (Standing Wave Ratio) meter this week. If I have a problem, I have been advised to leave the current cable and antenna in place. The suggestion is to run a new cable through the fuselage, looping it around the existing coax cable where possible and affixing a new antenna inside the vertical stabilizer in the space between the rudder and the rear fin bulkhead. Fidel at One Air Composites says there is generally enough clearance to avoid friction between a thin antenna and the front of the rudder.

On 08/09/2023 14:09, Mark628CA wrote:
>> You can check your stuff using a common SRW meter. But your new radio will certainly tell you if your antenna is bad
>
> I will be checking the cable and antenna with an SWR (Standing Wave Ratio) meter this week. If I have a problem, I have been advised to leave the current cable and antenna in place. The suggestion is to run a new cable through the fuselage, looping it around the existing coax cable where possible and affixing a new antenna inside the vertical stabilizer in the space between the rudder and the rear fin bulkhead. Fidel at One Air Composites says there is generally enough clearance to avoid friction between a thin antenna and the front of the rudder.

A SWR meter will only give you the SWR at the frequency selected on your
radio.

An Antenna Analyser such as a MFJ:
https://mfjenterprises.com/collections/rf-testing/type_antenna-analyzers+company_mfj#collection

(which I use) will allow you to see the best SWR available, but this may
not at the frequency you want!

Mid-airband is at 127MHz which requires a 22inch (give or take) 1/4
wave, or in a fin about 45 inches for a dipole. There is not always room
for this in a fin, so compromises may have to be made.

Many years ago, I replaced the coax in my LS3. IIRC, I taped the ends together and pulled the new cable through the existing holes in the fuselage bulkheads but I might have simply looped it around the existing cable. 30+ years ago. Can't remember for certain. You kids will understand some day.

Also installed a homemade center-fed dipole in the space between the rudder and vertical fin after confirming there was room. Taped it in temporarily and tried it. Worked well but highly directional. Did some crude field strength mapping and turns out (my interpretation) the existing antenna was likely acting as a parasitic element in an antenna array. Hence the directional pattern. Removed the new antenna. Added a BNC connector to the stub coming out of the existing antenna in the fin, connected it to the new cable, and all was well. Still don't know how much, if any, the new coax improved things. My SWR readings were not bad before or after.

A LOT of work and anxiety. Wouldn't do it again unless I had confirmation the coax was a problem. Worked through the small hole in the vertical fin bulkhead. No new holes cut in fuselage.

Chip Bearden
"JB"

Unfortunately, there does not appear to be any "easy" way to access the fin antenna for either removal or connector inspection. I guess what I will do first is check with an SWR meter. If the reading is reasonably OK, I will probably leave the antenna and cable in place and check again with the new radio. If there is an improvement in RX/TX, I will probably leave it alone. If not, a more complex solution will be considered. Just trying to keep things simple. You know, following the path of least resistance. (Humor for the "sparkys.")

On Friday, September 8, 2023 at 2:45:44 PM UTC-4, Mark628CA wrote:
> Unfortunately, there does not appear to be any "easy" way to access the fin antenna for either removal or connector inspection. I guess what I will do first is check with an SWR meter. If the reading is reasonably OK, I will probably leave the antenna and cable in place and check again with the new radio. If there is an improvement in RX/TX, I will probably leave it alone. If not, a more complex solution will be considered. Just trying to keep things simple. You know, following the path of least resistance. (Humor for the "sparkys.")
Your humor, "oh it Hz".
;-)

On Wednesday, September 6, 2023 at 5:53:11 AM UTC-7, Mark628CA wrote:
> I am thinking about upgrading my radio transceiver in my 40 year old Pegasus. By this time, I wouldn't be surprised if the coax cable to the fin antenna has degraded due to cracked insulation or something like that. Any suggestions about replacing the antenna and cable? Or should I just go with a dipole inside the (fiberglass) tail boom? I will test the system with an SWR meter and hope I don't have any issues, but just in case.....

An SWVR test is a somewhat crude measurement that gives you a gross indication. A far better test is time domain reflectometry (TDR). TDRs used to be very expensive instruments, but not necessarily so these days:
https://www.amazon.com/dp/B0825PZNJJ/ref=syn_sd_onsite_desktop_0?ie=UTF8&psc=1&pd_rd_plhdr=t

Tom 2G

Wow! The instrument is much smaller and less expensive than the
Hewlett-Packard oscilloscope I used in college back in '72.

Dan
5J

On 9/15/23 15:41, 2G wrote:
> On Wednesday, September 6, 2023 at 5:53:11 AM UTC-7, Mark628CA wrote:
>> I am thinking about upgrading my radio transceiver in my 40 year old Pegasus. By this time, I wouldn't be surprised if the coax cable to the fin antenna has degraded due to cracked insulation or something like that. Any suggestions about replacing the antenna and cable? Or should I just go with a dipole inside the (fiberglass) tail boom? I will test the system with an SWR meter and hope I don't have any issues, but just in case.....
>
> An SWVR test is a somewhat crude measurement that gives you a gross indication. A far better test is time domain reflectometry (TDR). TDRs used to be very expensive instruments, but not necessarily so these days:
> https://www.amazon.com/dp/B0825PZNJJ/ref=syn_sd_onsite_desktop_0?ie=UTF8&psc=1&pd_rd_plhdr=t
>
> Tom 2G

On Friday, September 15, 2023 at 3:04:08 PM UTC-7, Dan Marotta wrote:
> Wow! The instrument is much smaller and less expensive than the
> Hewlett-Packard oscilloscope I used in college back in '72.
>
> Dan
> 5J
> On 9/15/23 15:41, 2G wrote:
> > On Wednesday, September 6, 2023 at 5:53:11 AM UTC-7, Mark628CA wrote:
> >> I am thinking about upgrading my radio transceiver in my 40 year old Pegasus. By this time, I wouldn't be surprised if the coax cable to the fin antenna has degraded due to cracked insulation or something like that. Any suggestions about replacing the antenna and cable? Or should I just go with a dipole inside the (fiberglass) tail boom? I will test the system with an SWR meter and hope I don't have any issues, but just in case.....
> >
> > An SWVR test is a somewhat crude measurement that gives you a gross indication. A far better test is time domain reflectometry (TDR). TDRs used to be very expensive instruments, but not necessarily so these days:
> > https://www.amazon.com/dp/B0825PZNJJ/ref=syn_sd_onsite_desktop_0?ie=UTF8&psc=1&pd_rd_plhdr=t
> >
> > Tom 2G

Most people have no idea how much stuff they can pack into a VLSI (very large scale integrated) circuit these days, with the most complex having more than 100 BILLION transistors on a single chip. Bear in mind, that I worked with computers built with individual transistors hand-soldered into a circuit board, and integrated circuits with a few dozen transistors was considered revolutionary.

Tom 2G

Yup. Outside of college, I started by installing my own-built devices
in the back plane of a Nova 800 computer, a 16-bit, single-user
computer. It had 32K words of memory and a 19-inch rack mounted hard
drive of 5 MB. Imagine: Entering the bootstrap loader via the front
panel switches, to start from the paper tape reader.

We've come a long way...

Dan
5J

On 9/15/23 19:28, 2G wrote:
> On Friday, September 15, 2023 at 3:04:08 PM UTC-7, Dan Marotta wrote:
>> Wow! The instrument is much smaller and less expensive than the
>> Hewlett-Packard oscilloscope I used in college back in '72.
>>
>> Dan
>> 5J
>> On 9/15/23 15:41, 2G wrote:
>>> On Wednesday, September 6, 2023 at 5:53:11 AM UTC-7, Mark628CA wrote:
>>>> I am thinking about upgrading my radio transceiver in my 40 year old Pegasus. By this time, I wouldn't be surprised if the coax cable to the fin antenna has degraded due to cracked insulation or something like that. Any suggestions about replacing the antenna and cable? Or should I just go with a dipole inside the (fiberglass) tail boom? I will test the system with an SWR meter and hope I don't have any issues, but just in case.....
>>>
>>> An SWVR test is a somewhat crude measurement that gives you a gross indication. A far better test is time domain reflectometry (TDR). TDRs used to be very expensive instruments, but not necessarily so these days:
>>> https://www.amazon.com/dp/B0825PZNJJ/ref=syn_sd_onsite_desktop_0?ie=UTF8&psc=1&pd_rd_plhdr=t
>>>
>>> Tom 2G
>
> Most people have no idea how much stuff they can pack into a VLSI (very large scale integrated) circuit these days, with the most complex having more than 100 BILLION transistors on a single chip. Bear in mind, that I worked with computers built with individual transistors hand-soldered into a circuit board, and integrated circuits with a few dozen transistors was considered revolutionary.
>
> Tom 2G

You win, Tom. Hands down!

Dan
5J

On 9/17/23 22:20, 2G wrote:
> On Saturday, September 16, 2023 at 8:09:38 AM UTC-7, Dan Marotta wrote:
>> Yup. Outside of college, I started by installing my own-built devices
>> in the back plane of a Nova 800 computer, a 16-bit, single-user
>> computer. It had 32K words of memory and a 19-inch rack mounted hard
>> drive of 5 MB. Imagine: Entering the bootstrap loader via the front
>> panel switches, to start from the paper tape reader.
>>
>> We've come a long way...
>>
>> Dan
>> 5J
>> On 9/15/23 19:28, 2G wrote:
>>> On Friday, September 15, 2023 at 3:04:08 PM UTC-7, Dan Marotta wrote:
>>>> Wow! The instrument is much smaller and less expensive than the
>>>> Hewlett-Packard oscilloscope I used in college back in '72.
>>>>
>>>> Dan
>>>> 5J
>>>> On 9/15/23 15:41, 2G wrote:
>>>>> On Wednesday, September 6, 2023 at 5:53:11 AM UTC-7, Mark628CA wrote:
>>>>>> I am thinking about upgrading my radio transceiver in my 40 year old Pegasus. By this time, I wouldn't be surprised if the coax cable to the fin antenna has degraded due to cracked insulation or something like that. Any suggestions about replacing the antenna and cable? Or should I just go with a dipole inside the (fiberglass) tail boom? I will test the system with an SWR meter and hope I don't have any issues, but just in case.....
>>>>>
>>>>> An SWVR test is a somewhat crude measurement that gives you a gross indication. A far better test is time domain reflectometry (TDR). TDRs used to be very expensive instruments, but not necessarily so these days:
>>>>> https://www.amazon.com/dp/B0825PZNJJ/ref=syn_sd_onsite_desktop_0?ie=UTF8&psc=1&pd_rd_plhdr=t
>>>>>
>>>>> Tom 2G
>>>
>>> Most people have no idea how much stuff they can pack into a VLSI (very large scale integrated) circuit these days, with the most complex having more than 100 BILLION transistors on a single chip. Bear in mind, that I worked with computers built with individual transistors hand-soldered into a circuit board, and integrated circuits with a few dozen transistors was considered revolutionary.
>>>
>>> Tom 2G
>
> I even used a vacuum tube computer in college, an Alwac III-E at OSU:
> https://en.wikipedia.org/wiki/ALWAC_III-E#:~:text=The%20ALWAC%20III%2DE%20was,the%20Alwac%20III%20computer%2C%201959.
>
> Tom 2G

I counted on my fingers. That is a hands down winner.

On Monday, September 18, 2023 at 4:25:09 PM UTC-7, Dan Marotta wrote:
> You win, Tom. Hands down!
>
> Dan
> 5J
> On 9/17/23 22:20, 2G wrote:
> > On Saturday, September 16, 2023 at 8:09:38 AM UTC-7, Dan Marotta wrote:
> >> Yup. Outside of college, I started by installing my own-built devices
> >> in the back plane of a Nova 800 computer, a 16-bit, single-user
> >> computer. It had 32K words of memory and a 19-inch rack mounted hard
> >> drive of 5 MB. Imagine: Entering the bootstrap loader via the front
> >> panel switches, to start from the paper tape reader.
> >>
> >> We've come a long way...
> >>
> >> Dan
> >> 5J
> >> On 9/15/23 19:28, 2G wrote:
> >>> On Friday, September 15, 2023 at 3:04:08 PM UTC-7, Dan Marotta wrote:
> >>>> Wow! The instrument is much smaller and less expensive than the
> >>>> Hewlett-Packard oscilloscope I used in college back in '72.
> >>>>
> >>>> Dan
> >>>> 5J
> >>>> On 9/15/23 15:41, 2G wrote:
> >>>>> On Wednesday, September 6, 2023 at 5:53:11 AM UTC-7, Mark628CA wrote:
> >>>>>> I am thinking about upgrading my radio transceiver in my 40 year old Pegasus. By this time, I wouldn't be surprised if the coax cable to the fin antenna has degraded due to cracked insulation or something like that. Any suggestions about replacing the antenna and cable? Or should I just go with a dipole inside the (fiberglass) tail boom? I will test the system with an SWR meter and hope I don't have any issues, but just in case.....
> >>>>>
> >>>>> An SWVR test is a somewhat crude measurement that gives you a gross indication. A far better test is time domain reflectometry (TDR). TDRs used to be very expensive instruments, but not necessarily so these days:
> >>>>> https://www.amazon.com/dp/B0825PZNJJ/ref=syn_sd_onsite_desktop_0?ie=UTF8&psc=1&pd_rd_plhdr=t
> >>>>>
> >>>>> Tom 2G
> >>>
> >>> Most people have no idea how much stuff they can pack into a VLSI (very large scale integrated) circuit these days, with the most complex having more than 100 BILLION transistors on a single chip. Bear in mind, that I worked with computers built with individual transistors hand-soldered into a circuit board, and integrated circuits with a few dozen transistors was considered revolutionary.
> >>>
> >>> Tom 2G
> >
> > I even used a vacuum tube computer in college, an Alwac III-E at OSU:
> > https://en.wikipedia.org/wiki/ALWAC_III-E#:~:text=The%20ALWAC%20III%2DE%20was,the%20Alwac%20III%20computer%2C%201959.
> >
> > Tom 2G

I'm not sure what I "won" - old age?

On Sunday, September 17, 2023 at 9:20:21 PM UTC-7, 2G wrote:
> On Saturday, September 16, 2023 at 8:09:38 AM UTC-7, Dan Marotta wrote:
> > Yup. Outside of college, I started by installing my own-built devices
> > in the back plane of a Nova 800 computer, a 16-bit, single-user
> > computer. It had 32K words of memory and a 19-inch rack mounted hard
> > drive of 5 MB. Imagine: Entering the bootstrap loader via the front
> > panel switches, to start from the paper tape reader.
> >
> > We've come a long way...
> >
> > Dan
> > 5J
> > On 9/15/23 19:28, 2G wrote:
> > > On Friday, September 15, 2023 at 3:04:08 PM UTC-7, Dan Marotta wrote:
> > >> Wow! The instrument is much smaller and less expensive than the
> > >> Hewlett-Packard oscilloscope I used in college back in '72.
> > >>
> > >> Dan
> > >> 5J
> > >> On 9/15/23 15:41, 2G wrote:
> > >>> On Wednesday, September 6, 2023 at 5:53:11 AM UTC-7, Mark628CA wrote:
> > >>>> I am thinking about upgrading my radio transceiver in my 40 year old Pegasus. By this time, I wouldn't be surprised if the coax cable to the fin antenna has degraded due to cracked insulation or something like that. Any suggestions about replacing the antenna and cable? Or should I just go with a dipole inside the (fiberglass) tail boom? I will test the system with an SWR meter and hope I don't have any issues, but just in case.....
> > >>>
> > >>> An SWVR test is a somewhat crude measurement that gives you a gross indication. A far better test is time domain reflectometry (TDR). TDRs used to be very expensive instruments, but not necessarily so these days:
> > >>> https://www.amazon.com/dp/B0825PZNJJ/ref=syn_sd_onsite_desktop_0?ie=UTF8&psc=1&pd_rd_plhdr=t
> > >>>
> > >>> Tom 2G
> > >
> > > Most people have no idea how much stuff they can pack into a VLSI (very large scale integrated) circuit these days, with the most complex having more than 100 BILLION transistors on a single chip. Bear in mind, that I worked with computers built with individual transistors hand-soldered into a circuit board, and integrated circuits with a few dozen transistors was considered revolutionary.
> > >
> > > Tom 2G
> I even used a vacuum tube computer in college, an Alwac III-E at OSU:
> https://en.wikipedia.org/wiki/ALWAC_III-E#:~:text=The%20ALWAC%20III%2DE%20was,the%20Alwac%20III%20computer%2C%201959.
>
> Tom 2G
Me, too, but it was the IBM 709. We didn't get to even approach it, but just handed over a punched card deck to get our programs run. https://en.wikipedia.org/wiki/IBM_709