Reply
 
LinkBack Thread Tools Search this Thread Display Modes
  #1   Report Post  
Old September 30th 07, 12:26 AM posted to rec.radio.amateur.antenna
external usenet poster
 
First recorded activity by RadioBanter: Nov 2006
Posts: 85
Default Looking for groundwave propagation experience on 20m

Hi all

I am gradually working up to a project to TX telemetry from the car at
very low QRSS type data rates. Because of the unattended nature of the
system I am going to start using the HiFER freq of 13.56Mhz rather than
a "real" amateur allocation.

This of course means very low output power and no doubt a number of
other limitations for the TX. I really only need the system to work
predominately 10 miles from the base.

Yes I am aware of the frequency stability issues for very narrow band
signals. No doubt the vehicle bouncing around wont help either! May end
up using a Picollo type system where the freq difference between two
states is used to send data.

I am after some feedback and ideas about antenna systems to use. I
suspect the car TX antenna will only be a wire draped across the rear
window or a loaded broadcast antenna. The RX base antenna was going to
be just a dipole but I reasoned that this would be great for DX but
terrible for groundwave. Then thought about a vertical dipole, but am
concerned about the higher noise level. I'll probably end up trying
both. Initial tests are only going to be looking for a CW signal on a
waterfall.

Would also consider experimenting at a MedFER freq around 1700KHz but
base antenna efficiency might be pretty bad. There is also a lot more
RFI there.

Ideas welcome. If however you want to say it "wont work" please back it
up with some maths/calcs or your own direct experiences.

Cheers

Bob VK2YQA
  #2   Report Post  
Old September 30th 07, 01:48 AM posted to rec.radio.amateur.antenna
external usenet poster
 
First recorded activity by RadioBanter: Jul 2006
Posts: 797
Default Looking for groundwave propagation experience on 20m

here in the states we call 13.56MHz an ISM frequency. Meaning Industrial,
Scientific, and Medical. near any populated area you are liable to run into
diathermy machines, plasma ovens, rfid tag readers, and a host of other
noise generators there. i would suspect your environment may be similar.

for ground wave the vertical would probably be best, especially for
omnidirectional covereage... though a low dipole would likely work almost as
well.

frequency stability with modern equipment shouldn't be a problem, just be
sure to build everything nice an solid so it doesn't 'bounce around' and it
shouldn't be a problem... not like bouncing around tubes with mechanical
elements that would vibrate and move in the distant past.



"Bob Bob" wrote in message
news
Hi all

I am gradually working up to a project to TX telemetry from the car at
very low QRSS type data rates. Because of the unattended nature of the
system I am going to start using the HiFER freq of 13.56Mhz rather than
a "real" amateur allocation.

This of course means very low output power and no doubt a number of
other limitations for the TX. I really only need the system to work
predominately 10 miles from the base.

Yes I am aware of the frequency stability issues for very narrow band
signals. No doubt the vehicle bouncing around wont help either! May end
up using a Picollo type system where the freq difference between two
states is used to send data.

I am after some feedback and ideas about antenna systems to use. I
suspect the car TX antenna will only be a wire draped across the rear
window or a loaded broadcast antenna. The RX base antenna was going to
be just a dipole but I reasoned that this would be great for DX but
terrible for groundwave. Then thought about a vertical dipole, but am
concerned about the higher noise level. I'll probably end up trying
both. Initial tests are only going to be looking for a CW signal on a
waterfall.

Would also consider experimenting at a MedFER freq around 1700KHz but
base antenna efficiency might be pretty bad. There is also a lot more
RFI there.

Ideas welcome. If however you want to say it "wont work" please back it
up with some maths/calcs or your own direct experiences.

Cheers

Bob VK2YQA



  #3   Report Post  
Old September 30th 07, 02:02 PM posted to rec.radio.amateur.antenna
external usenet poster
 
First recorded activity by RadioBanter: Jul 2006
Posts: 326
Default Looking for groundwave propagation experience on 20m

On Sep 29, 8:48 pm, "Dave" wrote:
here in the states we call 13.56MHz an ISM frequency. Meaning Industrial,
Scientific, and Medical. near any populated area you are liable to run into
diathermy machines, plasma ovens, rfid tag readers, and a host of other
noise generators there. i would suspect your environment may be similar.

for ground wave the vertical would probably be best, especially for
omnidirectional covereage... though a low dipole would likely work almost as
well.

frequency stability with modern equipment shouldn't be a problem, just be
sure to build everything nice an solid so it doesn't 'bounce around' and it
shouldn't be a problem... not like bouncing around tubes with mechanical
elements that would vibrate and move in the distant past.

"Bob Bob" wrote in message

news


Hi all


I am gradually working up to a project to TX telemetry from the car at
very low QRSS type data rates. Because of the unattended nature of the
system I am going to start using the HiFER freq of 13.56Mhz rather than
a "real" amateur allocation.


This of course means very low output power and no doubt a number of
other limitations for the TX. I really only need the system to work
predominately 10 miles from the base.


Yes I am aware of the frequency stability issues for very narrow band
signals. No doubt the vehicle bouncing around wont help either! May end
up using a Picollo type system where the freq difference between two
states is used to send data.


I am after some feedback and ideas about antenna systems to use. I
suspect the car TX antenna will only be a wire draped across the rear
window or a loaded broadcast antenna. The RX base antenna was going to
be just a dipole but I reasoned that this would be great for DX but
terrible for groundwave. Then thought about a vertical dipole, but am
concerned about the higher noise level. I'll probably end up trying
both. Initial tests are only going to be looking for a CW signal on a
waterfall.


Would also consider experimenting at a MedFER freq around 1700KHz but
base antenna efficiency might be pretty bad. There is also a lot more
RFI there.


Ideas welcome. If however you want to say it "wont work" please back it
up with some maths/calcs or your own direct experiences.


Cheers


Bob VK2YQA- Hide quoted text -


- Show quoted text -


10 miles ground wave at 14 meg is going to be iffy....

denny / k8do

  #4   Report Post  
Old September 30th 07, 06:09 PM posted to rec.radio.amateur.antenna
external usenet poster
 
First recorded activity by RadioBanter: Sep 2007
Posts: 88
Default Looking for groundwave propagation experience on 20m

Bob Bob wrote:
Hi all

snip

Ideas welcome. If however you want to say it "wont work" please back it
up with some maths/calcs or your own direct experiences.

Cheers

Bob VK2YQA


I am able to work 40 to 45 miles from my mobile, using a 20m Hamstick in
the center of the sedan roof, to a friend who is using a ground mounted
vertical made from half a driven element from an old tribander. We are
both running 100W SSB, and the received signal levels are just enough
above the noise level to communicate. The terrain is relatively level,
and the path is from the western Minneapolis suburbs to a town southwest
of Minneapolis.

tom
K0TAR
  #5   Report Post  
Old September 30th 07, 09:48 PM posted to rec.radio.amateur.antenna
external usenet poster
 
First recorded activity by RadioBanter: Nov 2006
Posts: 85
Default Looking for groundwave propagation experience on 20m

Hi Denny

Pls elaborate.

Are you talking about a SSB voice situation or bandwidths that will
yield maybe 20-30dB better conditions? Also what power level are you
talking about?

Pls be specific.

Denny wrote:

10 miles ground wave at 14 meg is going to be iffy....

denny / k8do



  #6   Report Post  
Old September 30th 07, 09:51 PM posted to rec.radio.amateur.antenna
external usenet poster
 
First recorded activity by RadioBanter: Nov 2006
Posts: 85
Default Looking for groundwave propagation experience on 20m

Many thanks Tom

I can probably extrapolate from those numbers.

I haven't looked at the ISM/HiFER rules/regs but the QRSS type mode
itself is going to be maybe 20-30dB "better" than SSB. I guess I'd be on
par with your numbers at 100-200mW o/p
Cheers Bob

Tom Ring wrote:


I am able to work 40 to 45 miles from my mobile, using a 20m Hamstick in
the center of the sedan roof, to a friend who is using a ground mounted
vertical made from half a driven element from an old tribander. We are
both running 100W SSB, and the received signal levels are just enough
above the noise level to communicate. The terrain is relatively level,
and the path is from the western Minneapolis suburbs to a town southwest
of Minneapolis.

tom
K0TAR

Reply
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules

Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Any Experience? Professor Homebrew 0 January 4th 06 02:35 PM
Act Electronics experience Bugeyed Shortwave 2 September 15th 05 10:22 AM
A Most Humbling Experience K4YZ Policy 32 September 10th 05 10:00 PM
A Most Humming Experience AB8MQ Policy 1 September 8th 05 11:47 PM
HY Bad Experience [email protected] CB 12 July 18th 05 06:45 PM


All times are GMT +1. The time now is 05:57 PM.

Powered by vBulletin® Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 RadioBanter.
The comments are property of their posters.
 

About Us

"It's about Radio"

 

Copyright © 2017