To be or not to be...swr inline

[WROA675]

Happy Friday. Noobie question: keeping my surecom swr meter inline at all times, good or not so much? pros and cons?  I'm going to be reconfiguring my shack with the new arrival of a power station, TYT 9800P, and antenna switch box. A buddy of mine keeps his swr meter inline at all times and I was told by another that wasn't a necessary/good practice. So I'd like to hear more opinions and perspectives. TIA...73

[gortex2]

I do not. In my LMR world my meter costs many thousands more than the ham meter so in practice it gets used and put back in the box. At home I use my trusty BIRD when needed and put back in its leather case. If per say you did not have good grounding and took a hit to the antenna you will buy a new meter on top of radio. As long as your antenna is a solid unit it should not change much over time. I think checking them yearly is the only time I use my meter, unless something changes.

 

[tweiss3]

I do not either. I do check occasionally, but I don't see it necessary. I'm assuming you are talking the SW102, which does have 0.3db insertion loss, plus adapters/connectors, so leaving it inline isn't "free", but it's not that much loss. Up to you. Do you have your cables terminated directly in N connectors, or are you using adapters?

 

[WROA675]

44 minutes ago, tweiss3 said:

Do you have your cables terminated directly in N connectors, or are you using adapters?

My current cables are PL259 connecters, besides the pigtail (when using the SW102) no other adapters being used at the radio end. However, the RG58 does has one adapter at the antenna end, the LMR 400 has PL259 at both ends.

[mbrun]

The transmission path through the meter is passive, meaning the meter does not need to be powered on to pass signal. I keep mine inline with my GMRS base radio full-time and power it up periodically to confirm as appears well. The insertion loss is inconsequential at the present time. My amateur radio has one built-in, all I have to do is activate a menu item to show it.

It is ultimately your preference.


Michael
WRHS965
KE8PLM

[tweiss3]

8 minutes ago, Papatree said:

My current cables are PL259 connecters, besides the pigtail (when using the SW102) no other adapters being used at the radio end. However, the RG58 does has one adapter at the antenna end, the LMR 400 has PL259 at both ends.

If it was me, I'd leave it out. I was tuning up my repeater this weekend, verifying operation/programming/power/alignment before I move on to getting it on the air, and the little 2' N to PL259 jumper and one PL259 to N cable was worth 0.5db, add in the 0.3 for the meter, and that is on its way to significant loss.

[WRKC935]

9 hours ago, tweiss3 said:

= N cable was worth 0.5db, add in the 0.3 for the meter, and that is on its way to significant loss.

What do you consider significant loss and what do you feel is a truly significant loss ?   3dB,, maybe 6dB?

What if I told you I have a UHF repeater system that the stations are all turned down to 20 watts (they will NOT go lower)  had an antenna system loss (cable the combiner loss) of 12dB and talks 40 miles in all directions. 

 

[tweiss3]

25 minutes ago, WRKC935 said:

What do you consider significant loss and what do you feel is a truly significant loss ?   3dB,, maybe 6dB?

What if I told you I have a UHF repeater system that the stations are all turned down to 20 watts (they will NOT go lower)  had an antenna system loss (cable the combiner loss) of 12dB and talks 40 miles in all directions. 

 

That depends entirely on antenna height, and I would guess it is 250'+ in the air. Typically a home station is 50' or less, and short of going higher, I personally think it's better to take out losses that aren't necessary to every day operations. 

[marcspaz]

 

11 hours ago, Papatree said:

Happy Friday. Noobie question: keeping my surecom swr meter inline at all times, good or not so much? pros and cons?  I'm going to be reconfiguring my shack with the new arrival of a power station, TYT 9800P, and antenna switch box. A buddy of mine keeps his swr meter inline at all times and I was told by another that wasn't a necessary/good practice. So I'd like to hear more opinions and perspectives. TIA...73

 

I wouldn't be too worried about leaving the meter inline.  I leave meters inline on all my gear so I can monitor SWR and power while I am operating.  Any loss is almost non-existent, basically has no impact on system performance and knowing if my radio or antenna is starting to fail real-time is way more important to me.

A quick explanation as to why...  lets say you are hearing a weak station and you only have 3 bars (or S-units) on the radio's receive strength meter.  Assuming the radio's meter is configured correctly, you would have to decrease the receive signal to 1/4 of what you normally hear to have the meter drop to 2 bars.  That would be a dB loss of 6dB. 

The same is true for your transmit power.  If you are transmitting and the person on the other end receives your signal at 3 bars, you have to quadruple your output power to make that person's meter go up to 4 bars... or a 6dB gain in power.

Now, lets say you are running 50 watts from the radio and you have a 6dB loss to the antenna, that gives you 12.5 watts into the antenna.  It seems like a lot, but your signal only dropped one bar (1 S-unit).  If you have a 3dB loss, you would have a reduction in communications so small, that your radio can't measure and neither you are the other station will be able to detect by ear (assuming all else is equal). 

So, if your meter has 0.anything insertion loss, who cares?  It's not impacting your communications.

[PACNWComms]

When I started in RF communications several decades ago in the military, Bird/Thruline watt meters were only inserted during installation, and for yearly tests, to ensure the coax and antennas system was still serviceable. It was common to not leave a meter inline with the radio equipment. However, working with HF radio, it was common to ensure that a HF wattmeter was kept inline, as the radio gear was more expensive, the antenna being more critical, and the need to know the SWRmore important, meters were left inline. 

Fast forward to a few years ago, and I find myself making UHF Radio over Internet Protocol (RoIP) kits for connection of remote sites to a central hub station, and the Surecom SW102 is purchased to be a cheap inline meter. I begin to leave them inline for all of these kits. The people at the sites are not radio people, and travel is limited, so maintenance is only when something is completely broken. The cheap Surecom meter has a display, I can ask someone at each site to tell me what that meter says when the radio is keyed up. It shows SWR, frequency, and power, even providing a percentage. I now have them take a picture and send it to me. I now know what is going on coax, antenna and output power/SWR wise. I will continue to leave Surecom SW102 meters in UHF kits across the country. Their insertion loss is minimal, and they benefit me in a very positive way, as being a cheap check on the radio system in use at each site. 

Attached is a picture of a 25 watt UHF radio under test with a Surecom SW102, and even with many adapters in use,loss  and SWR is minimal. For actual installations, I made cables with the appropriate ends,to minimize loss even more, but this is an example of my own use of Surecom SW102 meters in use, in line with UHF radios. 

[mbrun]

 
 
I wouldn't be too worried about leaving the meter inline.  I leave meters inline on all my gear so I can monitor SWR and power while I am operating.  Any loss is almost non-existent, basically has no impact on system performance and knowing if my radio or antenna is starting to fail real-time is way more important to me.
A quick explanation as to why...  lets say you are hearing a weak station and you only have 3 bars (or S-units) on the radio's receive strength meter.  Assuming the radio's meter is configured correctly, you would have to decrease the receive signal to 1/4 of what you normally hear to have the meter drop to 2 bars.  That would be a dB loss of 6dB. 
The same is true for your transmit power.  If you are transmitting and the person on the other end receives your signal at 3 bars, you have to quadruple your output power to make that person's meter go up to 4 bars... or a 6dB gain in power.
Now, lets say you are running 50 watts from the radio and you have a 6dB loss to the antenna, that gives you 12.5 watts into the antenna.  It seems like a lot, but your signal only dropped one bar (1 S-unit).  If you have a 3dB loss, you would have a reduction in communications so small, that your radio can't measure and neither you are the other station will be able to detect by ear (assuming all else is equal). 
So, if your meter has 0.anything insertion loss, who cares?  It's not impacting your communications.

I thought I would inject something about meters. While a true IARU S-meter will exhibit the behavior described, none of my radios do, and most notably the Wouxun radios.

The meter on every radio I own with a meter has been measured in the past. Although varying slightly by model, the meter on every Wouxun radio I have tested will swing from zero to a full 9 bars with an input signal change of less than 14dBm when hooked directly to an FM signal generator. One unit will do so in as little as 6dBm, the rest are typically around 12dBm.

So whereas the meter on my ham FT-991A require a bigger change to move (1) S-Unit (at times close to 6dBm), the Chinese GMRS radios go from zero to full bars with very little signal change.

I bring this up because some folks using the cheap radios might think that when the meter on their radio changes by 1 bar they are indeed experiencing a 6dBm signal level change when in reality they may be experiencing less than 1dBm.

Regards,


Michael
WRHS965
KE8PLM

[marcspaz]

@mbrun I agree that many inexpensive radios don't have an accurate S-meter.  I did put a caveat in there, but only a single line.  Thanks for emphasizing that point. 

 

Side note.... I love to hear some people report "a real 59", not a contest 59. LoL

[PACNWComms]

Great point and an issue that has been expounded upon in previous threads about cheaper radios made in China, versus commercial grade radios made in Japan/Malaysia/Mexico/Israel. One poster even mentioned that their Chinese made radios ran "clean"......a point that I find hard to believe. I run a Radioddity DB20-G mobile in my daily commuter car, because it fits the dash cubby hole.....but I do not expect its signal meter to be accurate, or transmit to be perfect. In contrast, my picture above shows the Surecom SW102 meter connected to a Motorola XPR4550 UHF attached to a Zetron 6300 IP interface......I need better specs for real world professional use, and especially for RoIP interface equipment between sites. Something that a hobbyist may not need or afford for GMRS use, (the XPR4550 in this case is operating in analog mode). Great points above. 

[WROA675]

2 hours ago, PACNWComms said:

I run a Radioddity DB20-G mobile in my daily commuter car

Same...awesome little work horse.

[MichaelLAX]

2 hours ago, PACNWComms said:

I run a Radioddity DB20-G mobile in my daily commuter car, because it fits the dash cubby hole.....but I do not expect its signal meter to be accurate...

It's "signal meter" is from 1 to 10 dashes; how accurate could you expect it to be?!? 

[MichaelLAX]

9 hours ago, mbrun said:

So whereas the meter on my ham FT-991A require a bigger change to move (1) S-Unit (at times close to 6dBm), the Chinese GMRS radios go from zero to full bars with very little signal change.

And as I've informed you, Nigel Tufnel of Spinal Tap, has a guitar amp that goes up to 11! 

[PACNWComms]

3 hours ago, MichaelLAX said:

It's "signal meter" is from 1 to 10 dashes; how accurate could you expect it to be?!? 

Exactly, I do not expect it to be accurate. And the radios is made to be cheap.

[MichaelLAX]

1 hour ago, PACNWComms said:

Exactly, I do not expect it to be accurate. And the radios is made to be cheap.

I can't agree with your observation.

I believe this to be an incredible amount of radio efficiency for the price: It actually outperforms my Yaesu FT-857d on both 2 meters and 70 cm into the same Comet Tri-bander I have on my 2nd story roof.

I don't miss an S-Meter when I can turn off the squelch (Mon) and hear stations in the mud that I would not normally be able to communicate with.

I am actually considering replacing my 857d with the Yaesu FT-891 for 80 through 6 meters for $635, using the DB-20G (in my case denoted Anytone AT-779UV) for 2 meters and 70 cms and putting the 857d back in my backpack with my eBay collapsable portable antenna and going back on the road! Much cheaper than purchasing another 857d on the used market!

Inexpensive: yes; cheap - NO!

[axorlov]

On 1/7/2022 at 7:17 PM, marcspaz said:

Now, lets say you are running 50 watts from the radio and you have a 6dB loss to the antenna, that gives you 12.5 watts into the antenna.  It seems like a lot

It not only seems like a lot, it is a lot. It's 4x reduction in power. In space, it would mean reduction of communication distance in half. On the surface of this miserable planet it may be a difference between reliable comms and no comms at all.

I do not care what [poorly calibrated other dude's] S-meter says. I do not want to waste the power to warm up the atmosphere if this power can be put into signal.

 

[marcspaz]

2 hours ago, axorlov said:

It not only seems like a lot, it is a lot. It's 4x reduction in power. In space, it would mean reduction of communication distance in half. On the surface of this miserable planet it may be a difference between reliable comms and no comms at all.

I do not care what [poorly calibrated other dude's] S-meter says. I do not want to waste the power to warm up the atmosphere if this power can be put into signal.

 

 

I'm not going to knock anyone for wanting the most out of their system... but what you're saying about RF signals in space is not correct. There are so many variables that are involved and some pretty complex math to calculate.

 

As far as on earth, same thing applies.  Space weather, Geomagnetic storms, and atmospheric propagation combined with good antenna design plays a much larger role than power.

[gman1971]

Marc is BACK!!

[axorlov]

12 hours ago, marcspaz said:

Space weather, Geomagnetic storms, and atmospheric propagation combined with good antenna design plays a much larger role than power

That's often repeated, and often misunderstood. To overcome what you listed (storms, weather, etc), you need power. When antenna design and placement is not changing, power is what helps you to have [more] reliable communications.

[gman1971]

I've never done HF beyond some 4W CB in the late 80s/early 90s, so I don't have first hand experience with it. However, for VHF hi/UHF, the most important factor that determines RX range is receiver dynamic sensitivity and noise floor. For TX range, antenna radiation pattern and height are far more important than some power loss in the coax, followed quite closely by transmitter intermodulation distortion caused by other nearby high power TX... that is critical too... 

I personally think wasting 6dB is a waste, regardless of how good the rest of the system is. I can understand losing power to things one can't control, like planet alignment, sun flares, etc etc., but its under the radio operator control to make sure that the TX line is not burning 6dB through it...

G.

[axorlov]

20 minutes ago, gman1971 said:

For TX range, antenna radiation pattern and height are far more important

1. With antenna pattern and height is not changing, station transmits with power P, then it makes second transmission with power 4 x P? Which transmission going to be heard farther?
2. You are in the fringe zone of my station. Your S-meter (if you have one and you trust one) shows 0 bars. You still can hear me under current conditions with the specific noise floor and specific sensitivity. Now I reduce power 4 times. Will you still hear me?

Loss of 6dB is a waste. I would ignore loss under 1dB.

[marcspaz]

@axorlov As I mention before, I am not saying we shouldn't look for means to improve our losses.  I am simply trying to stress that the increase of power, even at 4 times your base wattage, does not have the significant impact in range of which you are implying.

For example, my son and I conducted real world tests in GMRS in 2020, while at our Florida home.  Specifically, we decided to test this theory, due to a conversation just like this with someone else from this forum.  We used a base antenna on the roof of the house, a mobile radio as a base station, 2 handhelds (1 base and 1 mobile), and a mobile radio in the Jeep

My Jeep essentially has no loss (less than 1 dB measured) with a 1/4 wave antenna.  At the house, I have measured loss of 4.1 dB going into a Diamond x300 repeater antenna which has a 6.9 db gain (tested) over my 1/4 wave antenna.

Starting with using handheld radios and using 0.800 watts (measured), we got 8.5 miles apart before the voices became unintelligible.  We switched to the mobile radios and upped the power to 5 watts (measured) and only made it to 8.8 miles before the audio became unintelligible.  From there we jumped directly to 42 watts (measured) and we hit a maximum distance of 10.5 miles of usable audio.

On that day, by increasing our power 53 times, we were only able to increase the usable range 2 miles, about a 20%.

 

I used that as an example for UHF and GMRS because it is directly related.  However, as we go lower in frequency, the performance increase becomes less and less because of how radio waves propagate.