Retevis RT97L portable repeater -- first impressions

[WRYZ926]

3 hours ago, WRTC928 said:

I'm puzzled about why I get different power readings with different antennas, though. If someone can explain it, please do. I'm still learning.

You are seeing loss from the coax and/or the antenna. Using quality coax and a good antenna with some gain will help overcome any loss. A dummy load will show a perfect match of 50 ohms, there won't be any loss with the dummy load.

@OffRoaderX was that a simple response? I know I have a ways to go to catch up to @SteveShannon 

[OffRoaderX]

1 minute ago, WRYZ926 said:

@OffRoaderX was that a simple response

less than 10 paragraphs and no big technical-sounding words, so you did good!

[WRYZ926]

I still have a ways to go before I reach @SteveShannon status 

[SteveShannon]

1 minute ago, WRYZ926 said:

I still have a ways to go before I reach @SteveShannon status 

I have no idea why anyone would want to. 

[LeoG]

1 hour ago, OffRoaderX said:

less than 10 paragraphs and no big technical-sounding words, so you did good!

Radio Dork?

[WRTC928]

9 hours ago, WRYZ926 said:

You are seeing loss from the coax and/or the antenna. Using quality coax and a good antenna with some gain will help overcome any loss. A dummy load will show a perfect match of 50 ohms, there won't be any loss with the dummy load.

@OffRoaderX was that a simple response? I know I have a ways to go to catch up to @SteveShannon 

I hadn't thought about loss in the cable causing an artificially high power reading, but now that you mention it...I guess it could.

Thanks.

None of the antennas I tested are likely to be the one I ultimately end up using, and I have 50' of LMR400 Ultraflex to feed it. There's always going to be some loss. All we can do is keep it to a minimum. As far as I know, anything you can easily coil up and carry is going to have quite a bit of loss at 462 MHz.

[WRYZ926]

1 hour ago, WRTC928 said:

I hadn't thought about loss in the cable causing an artificially high power reading, but now that you mention it...I guess it could.

Seeing  higher return power would be due to the antenna having a high SWR as it is reflecting power back down the coax.

That's why a dummy load should be used to test power output as the dummy load is a perfect 50 ohm match and should show a 1:1 SWR. That takes out coax loss and reflected power returning down the cable.

[SteveShannon]

1 hour ago, WRTC928 said:

I hadn't thought about loss in the cable causing an artificially high power reading, but now that you mention it...I guess it could.

Thanks.

None of the antennas I tested are likely to be the one I ultimately end up using, and I have 50' of LMR400 Ultraflex to feed it. There's always going to be some loss. All we can do is keep it to a minimum. As far as I know, anything you can easily coil up and carry is going to have quite a bit of loss at 462 MHz.

It seems I have a reputation to either change or uphold.  Here are the ten paragraphs and big technical sounding words.  Sorry.  
Lossy cable will always make your SWR appear artificially low when measured at the radio. If lossy cable is attenuating your forward power there will be less power that reaches the antenna and then whatever power is reflected by an imperfect impedance match is attenuated before if gets back to the radio.  So an RF power meter/SWR meter placed at the radio will see erroneously low reflected power, resulting in an erroneous calculation of forward power and an erroneously low calculation of SWR. If your radio has an ALC circuit, it limits output power as SWR increases and allows greater power if the SWR appears low.

Where are you measuring the power?  At the radio or at the antenna? If you want an accurate reading of the SWR of the antenna, you must read at the antenna feed point.  If you want to see how much power is reaching the antenna, measure it at the antenna feed point.  If you want to see how much power your radio is emitting, measure at the radio.  Sometimes it’s very helpful to measure power at both places at the same time to see the difference.

How are you measuring it? Some RF power meters are simply better than others. Expensive ones are calibrated to a standard for a specific frequency and power range.  Inexpensive ones may lose accuracy at different frequencies and power levels which can make things appear better or worse than they really are.

Are all measurements at the same transmit frequency? Our radios often (always?) have a range of power output levels that change at different frequencies.

[LeoG]

That's only 4 paragraphs...

[SteveShannon]

1 hour ago, LeoG said:

That's only 4 paragraphs...

I’m bad at counting also.  But at least I use an occasional period and paragraph breaks.  Every so often I see a post that is one long run-on free association. Those make my head hurt.

[WSHH887]

2 hours ago, SteveShannon said:

I’m bad at counting also.  But at least I use an occasional period and paragraph breaks.  Every so often I see a post that is one long run-on free association. Those make my head hurt.

Welcome to the new world of written communication brought to you by young people with limited education.