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eHam Forums => Elmers => Topic started by: KD2CJJ on August 17, 2012, 06:08:16 AM



Title: Do you NOT always keep your SWR meter inline due to insertion loss?
Post by: KD2CJJ on August 17, 2012, 06:08:16 AM
Im curious and contemplating which SWR meter to buy, and then realized thats just one more component to add to insertion loss (i have a balun midway to the antenna, a tuner, now SWR meter?) and wanted to know if you guys keep yours inline all the time OR only use it for specific tuning exercises.



Thanks


Title: RE: Do you NOT always keep your SWR meter inline due to insertion loss?
Post by: AC5UP on August 17, 2012, 06:26:20 AM
If your connectors and jumper cables are near perfect the insertion loss is inconsequential, and some folks enjoy seeing the meter verify the antenna id "OK" every time they push the TX button. Otherwise it's one more pair of connectors to work loose.

I'm going to assume the antenna tuner is an automatic type and you do not need an SWR bridge to keep it tweaked.


Title: RE: Do you NOT always keep your SWR meter inline due to insertion loss?
Post by: W5FYI on August 17, 2012, 08:07:15 AM
I'd rather have the miniscule insertion loss and be able to instantly see SWR anomalies than to not have it in line and miss a potentially costly problem. That's my 2¢ worth.


Title: RE: Do you NOT always keep your SWR meter inline due to insertion loss?
Post by: K8AXW on August 17, 2012, 08:47:30 AM
Quote
miss a potentially costly problem. That's my 2¢ worth.

And my 2 cents!  I've always left my SWR meter in line.  It's saved potentially costly mistakes many, many times during the past 55 years. 

Perhaps the only time to consider leaving it out is if you're running very low power.



Title: RE: Do you NOT always keep your SWR meter inline due to insertion loss?
Post by: WB6BYU on August 17, 2012, 09:16:15 AM
I leave it in place for HF, because I'm often readjusting the tuner and/or changing my
output power.

For VHF I don't:  I tune the antenna initially, then hook it straight to the rig and don't
worry about it unless it doesn't seem to be working right.


Title: RE: Do you NOT always keep your SWR meter inline due to insertion loss?
Post by: W8JX on August 17, 2012, 09:20:26 AM
I leave it in place for HF, because I'm often readjusting the tuner and/or changing my
output power.

For VHF I don't:  I tune the antenna initially, then hook it straight to the rig and don't
worry about it unless it doesn't seem to be working right.

I agree


Title: RE: Do you NOT always keep your SWR meter inline due to insertion loss?
Post by: KE3WD on August 17, 2012, 09:48:14 AM
I like to leave it inline as well, but I generally sswitch the meter over to indicate RF output power rather than SWR.  This is especially true if you purchase a Peak Reading power/swr meter and talk Sideband a lot.  You can see your RF peaks as you talk.  

Most hams don't seem to realize that power out drops when the SWR rises.  That means that if you are watching the Power Output meter and it should suddenly drop, first suspect might be a change in SWR for the worse.  


73


Title: RE: Do you NOT always keep your SWR meter inline due to insertion loss?
Post by: N4CR on August 17, 2012, 10:33:51 AM
My SWR meter has a feature in it that keeps my amp from keying when the SWR is above a preset level. That's a feature that is more important than insertion loss.


Title: RE: Do you NOT always keep your SWR meter inline due to insertion loss?
Post by: KA4POL on August 17, 2012, 10:35:50 AM
The losses are really neglectable. I am using it up to 23cm permanently. It allows me to recognize problems immediately.


Title: RE: Do you NOT always keep your SWR meter inline due to insertion loss?
Post by: K2DC on August 17, 2012, 10:57:51 AM
In over 30 years, I don't think I've taken the power/swr meter out of line for any reason except to check connections.  The insertion loss including connections (assuming properly installed connectors) is so low that it would likely be difficult to accurately measure without laboratory test equipment.  That's for HF.  For VHF and UHF, as posted earlier, I've never had one in line after properly tuning the antenna.

73,

Don, K2DC


Title: RE: Do you NOT always keep your SWR meter inline due to insertion loss?
Post by: W8JI on August 17, 2012, 12:15:30 PM
My power output indication goes up if the SWR goes up a little.

Most do.

I can't imagine worrying about the loss of a SWR meter, unless it is really poorly designed for the frequency range.

73 Tom


Title: RE: Do you NOT always keep your SWR meter inline due to insertion loss?
Post by: VE3FMC on August 17, 2012, 04:34:04 PM
Always in on HF
Always out on VHF


Title: RE: Do you NOT always keep your SWR meter inline due to insertion loss?
Post by: W9MMS on August 18, 2012, 05:12:27 AM
Get yourself a good Peak Envelope Power Meter/SWR and leave it inline.
A good PEP/SWR Meter is the N8LP LP100A meter. It is pricey, but well worth the investment in the long run, and it is very accurate.

http://www.telepostinc.com/lp100.html

http://www.eham.net/reviews/detail/5981

Just my $0.02 worth.

(((73))) Milverton.


Title: RE: Do you NOT always keep your SWR meter inline due to insertion loss?
Post by: STAYVERTICAL on August 18, 2012, 05:28:47 AM
When I'm using the FT897D with the FC40 remote ATU, I have found that an external SWR meter is not necessary for me.
The FT897D like many transceivers will indicate SWR (not very nicely - but its an indication), and the  remote ATU does a good job of matching.
But when I am using the TS430S, I always use an external SWR meter (Diamond SX600N) since otherwise if something goes wrong - smoke rising may be your first indicator.

Using an SWR meter internal to the rig, or an external one - is like insurance - it never seems necessary until something happens.
So I would definitely keep it in line.

73 - Rob


Title: RE: Do you NOT always keep your SWR meter inline due to insertion loss?
Post by: G3TXQ on August 20, 2012, 07:40:47 AM
I measure the insertion loss of my LP100 sense head as 0.022dB at 30MHz; I think I'll leave it in  ;)

Steve G3TXQ


Title: RE: Do you NOT always keep your SWR meter inline due to insertion loss?
Post by: G3RZP on August 20, 2012, 08:19:54 AM
In the days of VHF (low band) TV, when harmonics were a definite problem, it was best to have the low pass filter between the antenna and the SWR bridge. This was because the diodes in the bridge could produce enough harmonic energy to cause quite severe TVI. But because of the filter mismatch (there's always some!) the SWR never got as low as people felt it should. Since those were the days of tuned tube PAs, it didn't matter. But anywhere that's left with low band VHF TV, it might better to not leave the SWR meter in circuit.


Title: RE: Do you NOT always keep your SWR meter inline due to insertion loss?
Post by: G3TXQ on August 20, 2012, 08:30:31 AM
But anywhere that's left with low band VHF TV, it might better to not leave the SWR meter in circuit.
Or, perhaps, use an SWR meter that doesn't have diodes!

Steve G3TXQ


Title: RE: Do you NOT always keep your SWR meter inline due to insertion loss?
Post by: N4CR on August 20, 2012, 04:23:50 PM
I measure the insertion loss of my LP100 sense head as 0.022dB at 30MHz; I think I'll leave it in  ;)

Steve G3TXQ

How did you measure that? I've always wondered what the insertion loss was on my LP-100a.


Title: RE: Do you NOT always keep your SWR meter inline due to insertion loss?
Post by: G3TXQ on August 21, 2012, 12:26:52 AM
An S21 measurement on a 2-port VNA. It wont be accurate to 0.001dB, but it will be in the right "ball park"!

73,
Steve G3TXQ


Title: RE: Do you NOT always keep your SWR meter inline due to insertion loss?
Post by: F8WBD on August 22, 2012, 05:34:33 AM
My OHR QRP wattmeter is always in line with my FT-817. Use a short RG8x connection between the two. No tuner employed. Not necessary with my Par end fed wire.


Title: RE: Do you NOT always keep your SWR meter inline due to insertion loss?
Post by: AA4HA on August 22, 2012, 01:18:04 PM
Get yourself a good Peak Envelope Power Meter/SWR and leave it inline.
A good PEP/SWR Meter is the N8LP LP100A meter. It is pricey, but well worth the investment in the long run, and it is very accurate.

http://www.telepostinc.com/lp100.html

http://www.eham.net/reviews/detail/5981

Just my $0.02 worth.

(((73))) Milverton.

There seem to be quite a few Bird Model 43's floating around. They have very minimal insertion loss. I leave them in-line and usually have the slug rotated to look at reverse power. If I transmit and that needle jumps I know immediately that I have a major problem and shut down to go looking for a fried balun, coax issue, etc...

For about $40 you can buy a Peak Envelope Power (PEP) board that goes inside of a Bird wattmeter. It is a tremendously complicated kit to install. it attaches to the two panel meter lugs inside of the Bird 43, has a 9 volt battery, LED a power switch and another switch to go from PEP to normal operation. It took like an entire 10 minutes to install.

What is nice about Bird is that you can get slugs for anything from the AM broadcast band well up into the microwave spectrum. Also slugs are available at a variety of power ratings from 0-1 watt for a portable radio up to 0-10 kilowatts for commercial transmitters.

The slugs can also be the not so nice part as well. Prices on eBay can vary from $20 US up to $300 depending upon the supplier. You are not limited to just Bird slugs, there are several companies that make slugs that work in a bird wattmeter.

or, buy a Telewave with a rotary switch for power levels. Most folks are not calibrating a transmitter where you need to know within 2% of what the forward or reflected power is.

Oh, a major downside. You might want to download a little graph that shows you what the SWR is depending upon the forward vs. reflected power readings. You get both numbers just by rotating the slug 180 degrees in the socket. No crossed needles on this type of wattmeter or a little switch to go from FWD to REF.


Title: RE: Do you NOT always keep your SWR meter inline due to insertion loss?
Post by: K2UE on August 26, 2012, 05:16:46 AM
Insertion loss = Heat.  If it's not warm when you transmit, there's no point in removing it.


Title: RE: Do you NOT always keep your SWR meter inline due to insertion loss?
Post by: W8JI on August 26, 2012, 03:11:02 PM
An S21 measurement on a 2-port VNA. It wont be accurate to 0.001dB, but it will be in the right "ball park"!

73,
Steve G3TXQ

I thermally measured loss in a directional coupler I did some time ago.

It was ~.008 dB on almost all bands, just very slightly higher on ten meters than 160 or 80 meters. Nearly all loss was in the current transformer termination. It was a little difficult to not have the cables mess up the readings, but I think I got it pretty close. If the cables were sucking out more heat than I expected, then it would be less than .008 dB

I think .022 dB is high. That would be about 8 watts of heat at 1500 watts. I can't think of any meters that get that warm.





Title: RE: Do you NOT always keep your SWR meter inline due to insertion loss?
Post by: W0BTU on August 26, 2012, 05:00:36 PM
Insertion loss = Heat.  If it's not warm when you transmit, there's no point in removing it.

VERY well said, indeed! That is exactly right. This answer gets right to the heart of things.

People are always asking questions like this, wondering if they can make their signal stronger (or hear better) by doing something like this that won't make one bit of difference.

Some similar non-issues we hear discussed all the time are small losses in tuners, antenna switches, coax, or if connectors such as N connectors are better than PL-259s, or if our signal will be louder if we switch to some expensive coax on HF that they've seen advertised. (Or maybe stranded vs. solid wire, or insulated vs. uninsulated wire for our antennas.) And the list goes on.

In order for anything to lower the loss significantly, whatever we take out of the line has to be producing lots of heat that we can burn our fingers on, smell, or see the smoke. :-)

Leave your SWR meter in line and don't worry about it.


Title: RE: Do you NOT always keep your SWR meter inline due to insertion loss?
Post by: K7KBN on August 26, 2012, 08:09:36 PM
My advice is always the same:  try it and see how much difference it makes.


Title: RE: Do you NOT always keep your SWR meter inline due to insertion loss?
Post by: KG6MZS on August 27, 2012, 07:25:39 AM
Some similar non-issues we hear discussed all the time are small losses in tuners, antenna switches, coax, or if connectors such as N connectors are better than PL-259s, or if our signal will be louder if we switch to some expensive coax on HF that they've seen advertised. (Or maybe stranded vs. solid wire, or insulated vs. uninsulated wire for our antennas.) And the list goes on.

I understand what you are saying, but sometimes I think of the expression we have in backpacking: "Ounces make pounds."  The idea being that if you add up enough insignificant losses, they become significant.

That being said, my Palstar AT2K is always inline, so I always have the rig's meters and the cross needles on the tuner, even in bypass.


Title: RE: Do you NOT always keep your SWR meter inline due to insertion loss?
Post by: SWMAN on August 27, 2012, 11:31:16 AM
I dont ever keep mine inline, I just use the one on the radio which works fine. I use all single band tuned antennas so I dont really need it all of the time. 73 Jim W5JJG


Title: RE: Do you NOT always keep your SWR meter inline due to insertion loss?
Post by: W9MMS on August 27, 2012, 11:56:38 AM
Insertion loss = Heat.  If it's not warm when you transmit, there's no point in removing it.

VERY well said, indeed! That is exactly right. This answer gets right to the heart of things.

People are always asking questions like this, wondering if they can make their signal stronger (or hear better) by doing something like this that won't make one bit of difference.

Some similar non-issues we hear discussed all the time are small losses in tuners, antenna switches, coax, or if connectors such as N connectors are better than PL-259s, or if our signal will be louder if we switch to some expensive coax on HF that they've seen advertised. (Or maybe stranded vs. solid wire, or insulated vs. uninsulated wire for our antennas.) And the list goes on.



In order for anything to lower the loss significantly, whatever we take out of the line has to be producing lots of heat that we can burn our fingers on, smell, or see the smoke. :-)

Leave your SWR meter in line and don't worry about it.

Is this the "ELMERING" Forum?

>>>> People are always asking questions like this, wondering if they can make their signal stronger (or hear better) by doing something like this that won't make one bit of difference. <<<<
I guess there is really Dumb questions then! ???
I guess THOMAS EDISON's was also a question of "NON ISSUE" and did not make " one bit of difference " when he stumbled upon the Phonograph in Menlo Park?
>>> " The first great invention developed by Edison in Menlo Park was the tin foil phonograph. While working to improve the efficiency of a telegraph transmitter " <<<< end of quote.

The question was asked in earnest, which in my opinion (for what it's worth) makes it a legitimate question.
Sometimes, we (collectively) need to be a little bit more tolerant of others.

(((73))) Milverton.  


Title: RE: Do you NOT always keep your SWR meter inline due to insertion loss?
Post by: W0BTU on August 27, 2012, 12:51:26 PM
If my reply sounded intolerant, I didn't mean to. I was just trying to get a point across that many other people have also asked about on the forums.

Basically, if it doesn't get quite warm to the touch when we transmit (at say, 100 watts on CW or RTTY) for awhile, then the loss is nothing to be concerned about.

Even when we add up all the normal I2R losses in our connectors, switches, SWR and power meters together, the tiny fraction of a dB that it all adds up to is seldom going to make any difference in how well our signal gets heard at the other end.

Here is some food for thought: http://www.vk1od.net/transmissionline/concept/iltl.htm


Title: RE: Do you NOT always keep your SWR meter inline due to insertion loss?
Post by: W8JI on August 27, 2012, 04:51:18 PM
If my reply sounded intolerant, I didn't mean to. I was just trying to get a point across that many other people have also asked about on the forums.

Basically, if it doesn't get quite warm to the touch when we transmit (at say, 100 watts on CW or RTTY) for awhile, then the loss is nothing to be concerned about.

Not always.

If we lose 20-30 watts out of 1500 in an antenna tuner inductor, it can melt the inductor down.

If we lose 300 watts out of 1500 in a 100-foot long feeder, we may not notice.

How well something gets rid of heat matters just as much as how much heat we have to get rid of. :-)




Title: RE: Do you NOT always keep your SWR meter inline due to insertion loss?
Post by: K4RVN on August 29, 2012, 08:18:14 PM
W0BTU
I like that call BTU= a unit of heat.
 BTW, not knowing enough to judge the accuracy of your post, I found it to the point and not abrasive at all as you said in your following post with the clarification of your intention. It seemed to me like a good question and good answer.

Frank


Title: RE: Do you NOT always keep your SWR meter inline due to insertion loss?
Post by: K5TR on September 05, 2012, 09:00:55 AM
Im curious and contemplating which SWR meter to buy, and then realized thats just one more component to add to insertion loss (i have a balun midway to the antenna, a tuner, now SWR meter?) and wanted to know if you guys keep yours inline all the time OR only use it for specific tuning exercises.

I leave them in all the time.  Unless it is real junk it should not have any real loss.  They are made like a section of feed line with some sort of coupling
device (usually a coil) that is connected to the meter circuit.



Title: RE: Do you NOT always keep your SWR meter inline due to insertion loss?
Post by: WB6BYU on September 05, 2012, 05:02:56 PM
Just to clarify:  the reason I don't leave one in line for VHF (and sometimes for HF,
depending on the circumstances) has nothing to do with insertion loss.  That's
insignificant.

It is more to do with how often I plan to look at it.  On HF I actually use it quite often
as I change bands, etc.  On VHF I don't, so once I have checked that my antenna works
I put the meter back out in the barn to use for tuning some other antenna.