UHF penetration & path loss Q:
 

A few days ago I did a range check between
my base and handheld on 445 mhz and noted
the spot where I started to loose comms.

I came home and calculated xmtr power, feedline
losses & antenna gain. I figured I had about 114.4
watts ERP. I changed to 147.555 and re did the
test. Despite the fact that I figured I had 187.7 w
erp on VHF, I started loosing signal at the same
spot.

Base rig is a FT-857D, Handheld is a VX-7R with
the stock antenna. Base antenna is a Comet GP-6
up at 40' fed with Flexi 4xl coax. Terrain is flat.

Based on my data, either:

A) The difference in ERP is too small to matter, esp.
when you figure in UHF's higher path loss.

or

B) I need to do tests on both freqs at more than 1
location to establish a coverage pattern.


What do you guys think? A, B or ?

--
73's es gd dx de Ken KGØWX
Grid EM17ip, Flying Pigs #1055,
Digital On Six #350,
List Owner, Yahoo! E-groups:
VX-2R & FT-857

With your antenna at 40 feet you should have dropped out at about 8 1/2
miles. What was your actual distance?

"Ken Bessler" wrote in message
news:4nh9e.4900$mS1.1136@okepread04...
A few days ago I did a range check between
my base and handheld on 445 mhz and noted
the spot where I started to loose comms.

I came home and calculated xmtr power, feedline
losses & antenna gain. I figured I had about 114.4
watts ERP. I changed to 147.555 and re did the
test. Despite the fact that I figured I had 187.7 w
erp on VHF, I started loosing signal at the same
spot.

Base rig is a FT-857D, Handheld is a VX-7R with
the stock antenna. Base antenna is a Comet GP-6
up at 40' fed with Flexi 4xl coax. Terrain is flat.

Based on my data, either:

A) The difference in ERP is too small to matter, esp.
when you figure in UHF's higher path loss.

or

B) I need to do tests on both freqs at more than 1
location to establish a coverage pattern.


What do you guys think? A, B or ?

--
73's es gd dx de Ken KGØWX
Grid EM17ip, Flying Pigs #1055,
Digital On Six #350,
List Owner, Yahoo! E-groups:
VX-2R & FT-857

Noting the precision of your wattage calculations, I should have been more
specific in my answer in the previous message.
d(mi)=1.415 * sqrt antenna height in feet
so to get you down to the decimals 8.9492457782765135095568687307446 miles
This distance could be reduced by objects between you and your antenna.

a rule of thumb is sqrt 2* sqrt antenna height in feet = distance in miles.
"Ken Bessler" wrote in message
news:4nh9e.4900$mS1.1136@okepread04...
A few days ago I did a range check between
my base and handheld on 445 mhz and noted
the spot where I started to loose comms.

I came home and calculated xmtr power, feedline
losses & antenna gain. I figured I had about 114.4
watts ERP. I changed to 147.555 and re did the
test. Despite the fact that I figured I had 187.7 w
erp on VHF, I started loosing signal at the same
spot.

Base rig is a FT-857D, Handheld is a VX-7R with
the stock antenna. Base antenna is a Comet GP-6
up at 40' fed with Flexi 4xl coax. Terrain is flat.

Based on my data, either:

A) The difference in ERP is too small to matter, esp.
when you figure in UHF's higher path loss.

or

B) I need to do tests on both freqs at more than 1
location to establish a coverage pattern.


What do you guys think? A, B or ?

--
73's es gd dx de Ken KGØWX
Grid EM17ip, Flying Pigs #1055,
Digital On Six #350,
List Owner, Yahoo! E-groups:
VX-2R & FT-857

On Tue, 19 Apr 2005 22:16:57 -0400, "Fred W4JLE"
wrote:

Noting the precision of your wattage calculations, I should have been more
specific in my answer in the previous message.
d(mi)=1.415 * sqrt antenna height in feet
so to get you down to the decimals 8.9492457782765135095568687307446 miles
This distance could be reduced by objects between you and your antenna.

Whew. I'm glad you amended your remarks Fred. I was beginning to
worry about you.

Now, suppose there is a single deciduous tree located precisely half
way between the two points. Can you calculate whether it is leafed
out or not based on the added path loss?

Show your work [g].




a rule of thumb is sqrt 2* sqrt antenna height in feet = distance in miles.
"Ken Bessler" wrote in message
news:4nh9e.4900$mS1.1136@okepread04...
A few days ago I did a range check between
my base and handheld on 445 mhz and noted
the spot where I started to loose comms.

I came home and calculated xmtr power, feedline
losses & antenna gain. I figured I had about 114.4
watts ERP. I changed to 147.555 and re did the
test. Despite the fact that I figured I had 187.7 w
erp on VHF, I started loosing signal at the same
spot.

Base rig is a FT-857D, Handheld is a VX-7R with
the stock antenna. Base antenna is a Comet GP-6
up at 40' fed with Flexi 4xl coax. Terrain is flat.

Based on my data, either:

A) The difference in ERP is too small to matter, esp.
when you figure in UHF's higher path loss.

or

B) I need to do tests on both freqs at more than 1
location to establish a coverage pattern.


What do you guys think? A, B or ?

--
73's es gd dx de Ken KGØWX
Grid EM17ip, Flying Pigs #1055,
Digital On Six #350,
List Owner, Yahoo! E-groups:
VX-2R & FT-857

A few days ago I did a range check between
my base and handheld on 445 mhz and noted
the spot where I started to loose comms.

If you had crossed to other side of the road you would likely have
obtained different results.

"Fred W4JLE" bravely wrote to "All" (19 Apr 05 22:16:57)
--- on the heady topic of " UHF penetration & path loss Q:"

FW From: "Fred W4JLE"
FW Xref: aeinews rec.radio.amateur.antenna:28772

FW Noting the precision of your wattage calculations, I should have been
FW more specific in my answer in the previous message.
FW d(mi)=3d1.415 * sqrt antenna height in feet
FW so to get you down to the decimals 8.9492457782765135095568687307446
FW miles

Aw, you're just making it up now... anybody can see the last digit is
obviously wrong just looking at it!

A*s*i*m*o*v

.... If you're going to stand on thin ice, you might as well dance.