second PowerFlarm antenna

Can anyone tell me, how big of an impact antenna-receiver mismatch has? What if I use a European antenna in an US PowerFlarm (868 Mhz vs. required 916 Mhz).
Thank you in advance, Andrzej

On Friday, October 30, 2015 at 3:17:07 PM UTC-4, Andrzej Kobus wrote:
Can anyone tell me, how big of an impact antenna-receiver mismatch has? What if I use a European antenna in an US PowerFlarm (868 Mhz vs. required 916 Mhz).
Thank you in advance, Andrzej

By the way I forgot to add link to a very nice external antenna available in Europe.

http://www.air-store.eu/GAV-868

On Friday, October 30, 2015 at 12:17:07 PM UTC-7, Andrzej Kobus wrote:
Can anyone tell me, how big of an impact antenna-receiver mismatch has? What if I use a European antenna in an US PowerFlarm (868 Mhz vs. required 916 Mhz).
Thank you in advance, Andrzej

I think it would not be noticeable for receive only, being critical for transmit of course.

I would contact Don Pansier at DeltaPop, as his antennas look to be even lower drag than the one mentioned. http://www.deltapopaviation.com/Ultr...r_Antenna.html

It is always iffy to provide generic answers to generic questions without any data to back up statements.
If a mismatched antenna still works, depends on the system specifications (antenna and transmitter/receiver).

For the referenced antenna at http://www.air-store.eu/GAV-868 there is no data at all.
It is impossible to know how that antenna, intended for 868MHz, performs at 916MHz without evaluating the frequency characteristic of that antenna.

The antenna referenced by Bumper has some data.
The specified VSWR of 1.2 at 1030 to 1090 MHZ looks very good.
But you need to know the VSWR at 916MHz.
If that is still at 1.5 or so, it is still a good antenna for US Flarm.
If the VSWR at 916MHz increases beyond 2 it becomes questionable.
This means that more of the RF energy from the transmitter is being reflected by the antenna back into the transmitter (instead of radiated out) which will heat up the transmitter and might damage it.
It looks aerodynamically very sleek but I am not a aerodynamicist.
These antennas are monopoles, which means that they need a groundplane.
No big deal. You just need to know and take care of it by having foil / sheet metal / mesh underneath (e.g. aluminum roof flashing)

Antennas are reciprocal devices. With respect to performance, you will notice the same degradation effects of mismatch for receive as for transmit.
As mentioned above, the danger of mismatch at the transmit side is the reflection of energy back from the antenna into the transmitter, potentially damaging the transmit power amplifier. That is not an issue at the receive side.

3U

On Saturday, October 31, 2015 at 12:32:19 PM UTC-7, wrote:

The antenna referenced by Bumper has some data.
The specified VSWR of 1.2 at 1030 to 1090 MHZ looks very good.
But you need to know the VSWR at 916MHz.

3U

Don, at Delta Pop, was willing to work with me and provided a low drag transponder antenna with no male mounting screw thread. My idea being to use his antenna with threaded female mounting holes to which I'll add frangible brass thread. (Frangible in that the threaded rod will be grooved to more easily break proud of the antenna base. This will make the antenna "break away" so, if I get the theaded studs right, no damage will be done to glider or antenna in a trailer bonking incident. The broken threaded rod would then be easily removed, replaced and the antenna re-mounted. This project is on my middle burner.

With a reasonable amount of interest, Don may be willing to make his antenna centered on 915 Mhz - and with frangible mount if desired. Note that the antenna base is flat, and for mounting on most modern gliders will need to be mounted temporarily with cling wrap or other release agent so base gaps can be caulked with white silicone* or white epoxy putty (A-B, kind used for pool/boat repair), then removed and re-installed. Hole for coax fitting also slightly enlarged to facilitate break-away function with minimal risk of damage.

*silicone caulk smooths in nicely with wet finger.

On Sunday, November 1, 2015 at 1:10:20 AM UTC-5, bumper wrote:
On Saturday, October 31, 2015 at 12:32:19 PM UTC-7, wrote:

The antenna referenced by Bumper has some data.
The specified VSWR of 1.2 at 1030 to 1090 MHZ looks very good.
But you need to know the VSWR at 916MHz.

3U

Don, at Delta Pop, was willing to work with me and provided a low drag transponder antenna with no male mounting screw thread. My idea being to use his antenna with threaded female mounting holes to which I'll add frangible brass thread. (Frangible in that the threaded rod will be grooved to more easily break proud of the antenna base. This will make the antenna "break away" so, if I get the theaded studs right, no damage will be done to glider or antenna in a trailer bonking incident. The broken threaded rod would then be easily removed, replaced and the antenna re-mounted. This project is on my middle burner.

With a reasonable amount of interest, Don may be willing to make his antenna centered on 915 Mhz - and with frangible mount if desired. Note that the antenna base is flat, and for mounting on most modern gliders will need to be mounted temporarily with cling wrap or other release agent so base gaps can be caulked with white silicone* or white epoxy putty (A-B, kind used for pool/boat repair), then removed and re-installed. Hole for coax fitting also slightly enlarged to facilitate break-away function with minimal risk of damage.

*silicone caulk smooths in nicely with wet finger.

Bumper, silicone is something you do not want to use on a glider for this purpose. If you ever need repainting or repair, it is next to impossible to get proper paint adhesion to an area where silicone was previously applied. Silicone is next to impossible to remove completely. 3M has multiple polyurethane based product that are much more expensive but do not cause this problem and produce equal or better results.


Andrzej

On Sun, 01 Nov 2015 04:48:24 -0800, Andrzej Kobus wrote:

On Sunday, November 1, 2015 at 1:10:20 AM UTC-5, bumper wrote:
On Saturday, October 31, 2015 at 12:32:19 PM UTC-7,
wrote:

The antenna referenced by Bumper has some data.
The specified VSWR of 1.2 at 1030 to 1090 MHZ looks very good.
But you need to know the VSWR at 916MHz.

3U

Don, at Delta Pop, was willing to work with me and provided a low drag
transponder antenna with no male mounting screw thread. My idea being
to use his antenna with threaded female mounting holes to which I'll
add frangible brass thread. (Frangible in that the threaded rod will be
grooved to more easily break proud of the antenna base. This will make
the antenna "break away" so, if I get the theaded studs right, no
damage will be done to glider or antenna in a trailer bonking incident.
The broken threaded rod would then be easily removed, replaced and the
antenna re-mounted. This project is on my middle burner.

With a reasonable amount of interest, Don may be willing to make his
antenna centered on 915 Mhz - and with frangible mount if desired. Note
that the antenna base is flat, and for mounting on most modern gliders
will need to be mounted temporarily with cling wrap or other release
agent so base gaps can be caulked with white silicone* or white epoxy
putty (A-B, kind used for pool/boat repair), then removed and
re-installed. Hole for coax fitting also slightly enlarged to
facilitate break-away function with minimal risk of damage.

*silicone caulk smooths in nicely with wet finger.

Bumper, silicone is something you do not want to use on a glider for
this purpose. If you ever need repainting or repair, it is next to
impossible to get proper paint adhesion to an area where silicone was
previously applied. Silicone is next to impossible to remove completely.
3M has multiple polyurethane based product that are much more expensive
but do not cause this problem and produce equal or better results.

How about 24 hour epoxy glue thickened with microballoons to get a putty-
like consistency? That should be compatible with a glider airframe and is
a pretty standard and durable filler used in the model flying world for
gap filling and making fillets.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

At 12:48 01 November 2015, Andrzej Kobus wrote:
On Sunday, November 1, 2015 at 1:10:20 AM UTC-5, bumper wrote:
On Saturday, October 31, 2015 at 12:32:19 PM UTC-7,

w=
Note that
th=
e antenna base is flat, and for mounting on most modern gliders will need
t=
o be mounted temporarily with cling wrap or other release agent so base
gap=
s can be caulked with white silicone* or white epoxy putty (A-B, kind
used
=
for pool/boat repair), then removed and re-installed. Hole for coax
fitting=
also slightly enlarged to facilitate break-away function with minimal
risk=
of damage.
=20
*silicone caulk smooths in nicely with wet finger.

Bumper, silicone is something you do not want to use on a glider for this
p=
urpose. If you ever need repainting or repair, it is next to impossible
to
=
get proper paint adhesion to an area where silicone was previously
applied.=
Silicone is next to impossible to remove completely. 3M has multiple
polyu=
rethane based product that are much more expensive but do not cause this
pr=
oblem and produce equal or better results.


Andrzej

I think that the use of silicone calk in this way should be fine, the
original
poster said to cover the fuselage with cling wrap (cling film in the UK) or

similar during the application, the calk would only be in contact with the

glider once it was set, this should not cause the kind of problems you can
get
with silicone polish or grease.
Ben.
NB it would probably be better to use electronic grade sealant such as Dow

Corning 744 as the household / bathroom types contain acetic acid and can
corrode any metal parts.

On Friday, October 30, 2015 at 12:17:07 PM UTC-7, Andrzej Kobus wrote:
Can anyone tell me, how big of an impact antenna-receiver mismatch has? What if I use a European antenna in an US PowerFlarm (868 Mhz vs. required 916 Mhz).
Thank you in advance, Andrzej

Benedict is correct. No silicone caulk would be in contact with the glider before it is cured.

It would also be possible to "drape" cling wrap over the antenna itself, with only the two screw threads penetrating the plastic to mount the antenna - pull the wrap up snug and tape around the blade. Then the silicon will be applied between the antenna and fuselage (actually though, between the two layers of cling wrap, so not touching the glider. When cured, remove antenna and you have a nice form fitting silicone gasket.

I'm aware of the issue with regular RTV's acetic acid, being an old ex-Navy ET. Shouldn't be an issue with the RTV silicone used in the manner I described. Also aware of the supposed need to keep silicone in polishes away from glider finish, but that's another whole discussion that, after talking to Larry Mansberger years ago, I no longer worry about silicones in polish. Larry dismissed it out of hand, said he solvent cleans the surfaces prior to repair in any case and it was not an issue.

I purchased white A&B white epoxy putty to make my "gasket". It was Don, who makes the antennas, who suggested silicone would be easier. See:

http://www.amazon.com/Anderson-Epoxy.../dp/B0030CT6XM

bumper

On Sunday, November 1, 2015 at 7:11:23 PM UTC-5, bumper wrote:
On Friday, October 30, 2015 at 12:17:07 PM UTC-7, Andrzej Kobus wrote:
Can anyone tell me, how big of an impact antenna-receiver mismatch has? What if I use a European antenna in an US PowerFlarm (868 Mhz vs. required 916 Mhz).
Thank you in advance, Andrzej

Benedict is correct. No silicone caulk would be in contact with the glider before it is cured.

It would also be possible to "drape" cling wrap over the antenna itself, with only the two screw threads penetrating the plastic to mount the antenna - pull the wrap up snug and tape around the blade. Then the silicon will be applied between the antenna and fuselage (actually though, between the two layers of cling wrap, so not touching the glider. When cured, remove antenna and you have a nice form fitting silicone gasket.

I'm aware of the issue with regular RTV's acetic acid, being an old ex-Navy ET. Shouldn't be an issue with the RTV silicone used in the manner I described. Also aware of the supposed need to keep silicone in polishes away from glider finish, but that's another whole discussion that, after talking to Larry Mansberger years ago, I no longer worry about silicones in polish. Larry dismissed it out of hand, said he solvent cleans the surfaces prior to repair in any case and it was not an issue.

I purchased white A&B white epoxy putty to make my "gasket". It was Don, who makes the antennas, who suggested silicone would be easier. See:

http://www.amazon.com/Anderson-Epoxy.../dp/B0030CT6XM

bumper

Quicker and easier method is to wax the fuselage surface, mix up a small portion of aerodynamic fairing compound (body filler)squeeze the whole thing into place for a few minutes, remove and knife trim filler to shape. For the fastideous, white hardener is available.
Yes- you do need to protect threads and stuff.
UH