Coax loss

[KD2GOE]

Well I did a power test on 446mhz on 50'..
Testing at the radio I got 23watts
Testing at the other end I get 13w
I am loosing 10w through coax loss....
Is this excessive or something normal?

This is the coax
http://www.davisrf.com/buryflex.php

 

[sp5it]

Your meter is fooling you.

 

[KD2GOE]

Your meter is fooling you.

How so??

 

[sp5it]

Play with https://ac6la.com/tldetails1.html
You'll find out.
Mike

 

[Shadetree Mechanic]

Play with https://ac6la.com/tldetails1.html
You'll find out.
Mike

Thanks for the link, I often find myself thinking about RF power transmission.

 

[KC9Q]

GOE,

23 Watts = +43.6173 dBm
Connector Loss = -0.1 dB
50 ft BuryFlex = -1.4 dB
Connector Loss = -0.1 dB

Total Gain = 43.6173 dBm
Total Loss = -1.6 dB

ERP = 43.6173 – 1.6 = 42.0173 dBm
= 15.9121 Watts

13 Watts / 15.9121 Watts = 0.816988
100 x .816988 = 81.6988 %
100% – 81.6988% = 18.3012% (~18.3%)

You're measuring 13 Watts which is about a 18.3% higher loss than what should be.
Either your transmission line assembly has more loss than expected, or there is
a 18.3% error introduced by the meter, or a combination of the two.

Mike

 

[KD2GOE]

ok so you would be expecting a reading of 15w out the other end?

Well my meter is a MFJ-847 seems right or close with my TS-2000 and with 3 HT's that are ratted at 4w
The radio being tested is a 25w Kenwood TK-840 i have 4 of them and they read 23~25W

it maybe a compound of the 2.
all tests where preformed with a dummy load..

 

[KD2GOE]

Play with https://ac6la.com/tldetails1.html
You'll find out.
Mike

I put LMR400 in and 23w in and it is saying 12.2 out...

 

[sp5it]

Your antenna have R=250 Ohm? Does not have 50 either, but should be close.

 

[KD2GOE]

Your antenna have R=250 Ohm? Does not have 50 either, but should be close.

ahhhh yeah i don't know how to use this program..


well my Friend has a bird meter he is going to swing by and we will test with that...

 

[sp5it]

Use dummy load instead of antenna. You should see coax loss.
Mike

 

[543_Dallas]

Well I did a power test on 446mhz on 50'..
Testing at the radio I got 23watts
Testing at the other end I get 13w
I am loosing 10w through coax loss....
Is this excessive or something normal?

This is the coax
http://www.davisrf.com/buryflex.php

According to this calculator

https://www.qsl.net/co8tw/Coax_Calculator.htm

you're about 3 watts off. That's good enough. You have to be using a dummy load for accurate readings. When I tested the lmr400 to my vhf/uhf antenna with a bird 43 I found this calculator to be very close.

 

[Road Squawker]

A little "secret" that the coax companies don't (actively) tell you is the Db loss/100 feet is into a 50 ohm load.

 

[W4KVW]

Well within the accuracy of most wattmeters with that reading. Even within the Bird meters accuracy.

SIX-SHOOTER

 

[KD2GOE]

Use dummy load instead of antenna. You should see coax loss.
Mike

I don't think I was clear enough I was using a dummy load not the antenna
I did that...