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To be or not to be...swr inline


WROA675
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40 minutes ago, gman1971 said:

Wrong, measured data proves that adding 6dB inside a forest did NOT yield double the range, adding 10dB on a more favorable frequency with a 5/8 wave antenna (vs a rubber duck) increased range only by about 2.7 times, at best, so a 6dB increase will NOT double the range inside a forest as you claim. Now, the data did prove that adding 120 feet of antenna elevation showed at least a four-fold increase in range, from <4 miles to at least 16 miles.  Do you have any data collected? or you just guess stuff up with some formulas? Back at a previous job I used to joke that everything done in simulation is doomed to succeed...

And where did you say that you ask? What about you just told Marc that going from .8W to 42W will likely experience a 2000% percent increase in distance.... , so adding x52 times the power yields a 2000% range increase too...  do you really guess this stuff?

I guess sometimes not even sleep can fix the problem, darling...

G.

Look, Gman

I do not argue with the importance of the height, ok? Do you understand that? Never I said, that your glorious beautiful 120' mast has no effect or has little effect. Can we, sort of, seal that? Because you keep bringing that back all the time. Yes, you have a long, tall, fat, strong mast. OK! Can we put it aside now? With the note, that it was you, my friend, who totally invented the argument about the mast just to brag about it.

You keep accusing me of magic bro-formulas, but do not seem to understand how electromagnetic field works and throw terms like "Fresnel clearing" without any clue, because it absolutely not applicable to what we are talking about. Just stop using words that you do not understand.

I stand behind my claim that in the forest, on UHF, quadrupling the power from 5W to 20W doubles the distance from 0.5 mile to 1 mile. This is proven and tested by yours truly many times. In European plains and in California coastal forest. I did not have notaries, or Guiness book recorders to fix it officially, sorry. But talk to any hunter here, and they will confirm to you that moving from 1W FRS to 4W GMRS radio doubles the distance in the forest.

Keep Marc out of our small tiny scuffle here. He is a good guy.
With that said, I stand behind my claim that 0.8W -> 42W will increase distance from around the corner to 8 blocks. The number "2000%" is an educated guess. Want to show how wrong I am? Go measure the average city block and the "around corner" distance, have 2 witnesses to sign the affidavit, and if I'm off by more than 1dB, I will send you a pair of used earplugs as a symbolic token of me being wrong on that point.

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Great convos folks, such good information shared that I wish it had its own thread so more people might be able to benefit from it, as well...

Like so many other topics I've seen when the the thread goes off-topic, though relevant to the conversation, so many nuggets of wisdom and insight I feel are lost to the the rest of the community that aren't following said thread.

That said, the power supply is here and my TYT TH-9800P should be arrive tomorrow and I've decided to keep my Surecom SW102 in-line on my base station. Thank you all for the tips and sharing your experience and knowledge.

73

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Great convos folks, such good information shared that I wish it had its own thread so more people might be able to benefit from it, as well...
Like so many other topics I've seen when the the thread goes off-topic, though relevant to the conversation, so many nuggets of wisdom and insight I feel are lost to the the rest of the community that aren't following said thread.
That said, the power supply is here and my TYT TH-9800P should be arrive tomorrow and I've decided to keep my Surecom SW102 in-line on my base station. Thank you all for the tips and sharing your experience and knowledge.
73

Papatree,

I took some S21 measurements of the inline SWR arrangement I am using in my shack that you might find helpful.

Scenario consists of a 3-Foot RG-58 cable with PL-259 on each end, an SW-102 meter, and PL-259 to BNC adapter. Insertion loss of the whole assembly for GMRS = 1dB.

First image is the test configuration.

322a6514c199908518f45abb76f22611.jpg

2nd image represents insertion loss from 460-470MHz.
0b3c0760de121b89173ce4e10303fd41.jpg

Third image represents insertion loss from 50MHz to 900MHz.

34c77383312d466ceb469715f39873bb.jpg

As you can see, insertion loss is less that 1dB at and below GMRS frequencies, but gets a bit wonky over 500MHz.

Thought you might appreciate seeing this.

Yeh, the pictures are a little dark, but you get the picture. :)
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22 hours ago, mbrun said:

Scenario consists of a 3-Foot RG-58 cable with PL-259 on each end, an SW-102 meter, and PL-259 to BNC adapter. Insertion loss of the whole assembly for GMRS = 1dB.

Very nice. I like when pictures are posted instead of just seeing typed text and having to take someone's word for whatever is being discussed. Seeing this, I may buy more SW102 meters for some of my other UHF installs.....most of them are under 500 MHz. Thank you for posting.

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On 1/9/2022 at 5:53 PM, gortex2 said:

Love my old Motorola 2670 for hobby stuff at home but my Anritzu LMRMaster is a sweet box to carry to tower sites. I can almost throw it in my backpack. Can't do that with the 3920 :)

 

Actually Anritsu sells a backpack for that monitor to carry it (way over priced Swiss bag with their logo sewn in it).  Bag carrys the monitor and a medium sized laptop and the needed cables and bits.  You are talking a 412 right?

 

With regard to the dB discussion.  I think we need to lay out that it's not as simple as I need more dB to talk farther or a loss of X dB is or isn't significant.  As I mentioned before I have a system that the transmitters are turned down to 20 watts, because thats as low as they will go and they still talk farther than they hear from a separate antenna that is 30 feet above the transmit antenna.  That system has a cable and combiner loss of something like 9 or 12 dB.  But the 416 antenna at the top of the coax has 12 dB of gain so it's a wash.  And the receive antenna goes into a tower top amplifier to eliminate the cable line loss to boot. 

Someone mentioned the noise floor which is a really good point.  I can hear better from my tower at 240 feet than the 550 foot height (tower is 900) due to the noise floor being higher. And they are only 10 miles apart.  

Terrain has a TON to do with it as well.  And this is where you get height gain.  Now one needs to understand that a 6 Dbi gain antenna is going to have the SAME gain no matter the height. But what it's radiating through (whats between you and the tower) has a huge effect on the signal that gets to you.  The rule of thumb is every time to double the height, it's like adding 6dB of signal level increase.  Perspective on that is for every 3 dB of increase the power level doubles.  So a 10 watt radio increased 3dB is no 20 watts.  But dB math is logarithmic.  so 6 dB is not 30 watts it's 40 watts.  10 doubles to 20 and 20 doubles to 40.  So if you antenna is at 20 feet and you add 20 feet of tower it's like you went form 10 watts to 40 watts.  Here's the part that is REALLY important.  If you have a 40 watt signal coming out of a unity gain antenna.  A portable radio may hear you very well, but that's doesn't mean it can be heard by your transmit antenna at 20 feet.  Where if you are running 10 watts or even 2 watts, but are 40 feet up you will hear that portable radio and you can both communicate to each other.  Of course cable loss comes into play when it's doubled in length, but using the correct cable for the height, meaning it has less loss than the perceived gain due to the height increase, you will get better performance out of the antenna system as a whole.

 

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@WRKC935 Yes the 412. Love the box other than a couple analog features they left out. I have one back pack that fits it well but normally just toss it in a small pelican case and carry it with the phase stable cables. 

For the rest of the conversation the other thing folks are not remembering is these CCR radios have very wide filtering aka none for GMRS. Using a CCR base/portable and inferior cable and antenna's doesn't do what a commercial LMR radio and equipment will do (regardless of band). Noise floor is worse on a CCR especially as height increases. Just something to remember. I would suspect swapping out the TYT or Wuxon mobile for a XPR or CDM you will see the difference. 

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3 hours ago, gortex2 said:

For the rest of the conversation the other thing folks are not remembering is these CCR radios have very wide filtering aka none for GMRS. Using a CCR base/portable and inferior cable and antenna's doesn't do what a commercial LMR radio and equipment will do (regardless of band).

All of the radios I have I try to get the service manuals for them along with the operators manuals. Being an engineer I look through the schematics at times to see what makes a specific radio "tick" so to speak.

What I've found is just about, if not all, the commercial LMR radios I have use some kind of turntable front end filtering.  Those filters are typically before the first IF stage and acts as a pre-filter to improve the image response and the possible desense of the IF amplifier chain after the filters.

One of two techniques I've seen used are varactor diodes or variable inductance chokes. Both are "biased" by an output from the micro running the radio. As the frequency is changed the front end filter is electrically tuned to match the programed RX frequency.

The reason why CCR's are so cheap as you pointed out the front end filtering is minimal. This isn't just a problem with CCR's however. Many Ham HT's, from name brand manufactures, suffer from the same problem. As Hams we like the idea of a wide RX range for scanning etc. however that comes at a price, a wide open front end. To add in the fancy tuneable front end filters adds cost and complexity to the radio. 

To show you what is in some of the CCR's I found a schematic, reportedly, for the commonly mentioned UV-5R. I'm going to guess that derivatives of this radio the schematic won't look too much different. After all what did you expect to see in a radio that sells for about the same price as a kid's FRS bubble pack toy radio?

Oh, the harmonics on TX suck too. If you'll notice some of the harmonic tests were done at a load impedance of 25 ohms, not the expected nominal 50 ohms. At 25 ohms that would correspond to an SWR of 2:1 so the party doing the testing wanted to see if the harmonic content was SWR dependent.

 

SCHEMATIC Baofeng UV-5R.pdf UV-5R VHF Harmonics Test.pdf

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15 hours ago, gortex2 said:

@WRKC935 Yes the 412. Love the box other than a couple analog features they left out. I have one back pack that fits it well but normally just toss it in a small pelican case and carry it with the phase stable cables. 

For the rest of the conversation the other thing folks are not remembering is these CCR radios have very wide filtering aka none for GMRS. Using a CCR base/portable and inferior cable and antenna's doesn't do what a commercial LMR radio and equipment will do (regardless of band). Noise floor is worse on a CCR especially as height increases. Just something to remember. I would suspect swapping out the TYT or Wuxon mobile for a XPR or CDM you will see the difference. 

Absolutely, a TYT to XPR5550e swap yields a range from <2 miles to 18 miles, simplex... on a two bay dipole.

Also, no filtering in the front end means TX IMD, which will further trash the range of the radio. Again, those things are that, garbage.

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16 hours ago, gman1971 said:

XPR5550e

I'm still using my CDM1550LS+, and need to get a good antenna connected to my XPR5550e. Assembled it with a power supply, but still only using a cheap Lair magnet mount 1/4 wave antenna. Does receive well though, it is considered the best for receive (XPR5550e), and they work well alongside other radios in their selectivity. 

+1 on encouraging people to get a XPR5550e if they can afford it, and CPS, programming cable, etc. 

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1 hour ago, PACNWComms said:

I'm still using my CDM1550LS+, and need to get a good antenna connected to my XPR5550e. Assembled it with a power supply, but still only using a cheap Lair magnet mount 1/4 wave antenna. Does receive well though, it is considered the best for receive (XPR5550e), and they work well alongside other radios in their selectivity. 

+1 on encouraging people to get a XPR5550e if they can afford it, and CPS, programming cable, etc. 

Nice. I really liked the CDM750s when I was testing them, I even used the Tuner program to make the SQL open at pretty much noise floor level. The Professional series radios (CDM, HT1250, etc) are, IMO, probably the greatest FM VHF/UHF radios you can buy for the price. They will outperform anything CCR made... and you can repair them too, rather than throw them in the trash...

The selectivity on the 5550e is quite impressive. I can key a 5W XPR7550e portable on an adjacent channel, ~25khz apart, from just few feet away and the RX light won't even blink on the 5550e.

Not the case on any other radio I own, including the EVX radios... where the RX LED will blink when you try that... meaning is desensing and thus RX range will be crap.

G.

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I had to prove to some people about a few years ago that a Trbo based radio in digital mode was selective enough to not desense when a similar Trbo radio was transmitting in analog mode right next to it and their antennas being colocated (within maybe a foot apart). This test was with 25 watt radios, but was later repeated with 40 watt UHF versions (XPR4550's), both with SW102 Surecom wattmeters installed in line to see that they were putting out the wattage they were spec'ed for. Some people were amazed at the selectivity of each. Now Trbo XPR4550's are the bare minimum for mobiles, with XPR5550e's being the more expensive option. Bang for the buck, the best money you can spend on a mobile.

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1 hour ago, Muzic2Me said:

Im new to the game .....So if purchased an Ed Fong UHF antenna that has worked well for my HT and is tuned already for 462 I should not really need to check anything, correct? IS the SWR meter for checking exactly what?

I use the Surecom SW-102 for my mobile/base and the Surecom SW-33 for the HTs.

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Im new to the game .....So if purchased an Ed Fong UHF antenna that has worked well for my HT and is tuned already for 462 I should not really need to check anything, correct? IS the SWR meter for checking exactly what?

As a general rule you do not need to have an SWR meter when purchasing and using a purpose-built antenna like the Ed-Fong and a number of others. However, as you will learn, having some basic test equipment in your radio tool box can be incredibly helpful when installing a radio and antenna system, confirming operation and when trying to diagnose problems. In the consumer radio world, the SWR meter is probably the simplest and most fundamental of all radio tools. In my view however, you should plan to get one, and learn how to use it.

To second question, the SWR is checking exactly what? I could give you a detailed explanation, but I thing I will defer you to youtube and google as there is far more out there that will do your question justice then any simple answer I can give here on the forum. In a nutshell, the SWR meter is used to gives you a sense of how well you antenna system matches (is tuned) to what the radio is expecting to experience on the frequencies you’ll be operating on. If it is not tuned well or is defective your radio could perform poorly or perhaps even be damaged.

Google ‘What is SWR’.


Michael
WRHS965
KE8PLM
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46 minutes ago, mbrun said:


As a general rule you do not need to have an SWR meter when purchasing and using a purpose-built antenna like the Ed-Fong and a number of others. However, as you will learn, having some basic test equipment in your radio tool box can be incredibly helpful when installing a radio and antenna system, confirming operation and when trying to diagnose problems. In the consumer radio world, the SWR meter is probably the simplest and most fundamental of all radio tools. In my view however, you should plan to get one, and learn how to use it.

To second question, the SWR is checking exactly what? I could give you a detailed explanation, but I thing I will defer you to youtube and google as there is far more out there that will do your question justice then any simple answer I can give here on the forum. In a nutshell, the SWR meter is used to gives you a sense of how well you antenna system matches (is tuned) to what the radio is expecting to experience on the frequencies you’ll be operating on. If it is not tuned well or is defective your radio could perform poorly or perhaps even be damaged.

Google ‘What is SWR’.


Michael
WRHS965
KE8PLM

Thanks @mbrun.No better time to play around and learn with one I guess when the stuff is working right, ey.

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On 1/26/2022 at 3:44 PM, WROA675 said:

Surecom SW-33 for the HTs

I'll have to look into that model as a second unit. Currently, I have been using my SW-102 for handhelds by attaching the metal plate for a ground plane and removing the thumb stud, butit  is a bit tedious. It does work though.

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As @mbrun said. Usually you don't need anything adding further losses to the feedline, but when you use the cheap stuff you actually do, because the SWR always creeps up due to many factors, usually due to poorly manufactured antennas/cables/connectors... been there, done that.

G.

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So, one of the reasons I leave a meter inline actually came true yesterday, on my Ham gear.

 

I was using my VHF radio with a 200w amp.  I have a Watt/VSWR meter between the radio and the amp and another between the amp and the antenna.  With no warning and with zero indication other than the meter, my output power on my amplifier shot up to well over 300w, running about 70% more power than designed.

 

What likely happened is, there may be a cold/broken solder joint on a ground circuit for the final stage power regulator.  Instead of nuking my amp and possibly having a fire at my desk by continuing to use the amp (because without the meters I wouldn't have known), the meters helped me catch the problem immediately.  So now, instead of an $800 loss for the amp and potential untold damage to my home... I most likely will fix my amp for free.

 

Sometime we are prioritizing the wrong potential losses.

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4 minutes ago, marcspaz said:

So, one of the reasons I leave a meter inline actually came true yesterday, on my Ham gear.

 

I was using my VHF radio with a 200w amp.  I have a Watt/VSWR meter between the radio and the amp and another between the amp and the antenna.  With no warning and with zero indication other than the meter, my output power on my amplifier shot up to well over 300w, running about 70% more power than designed.

 

What likely happened is, there may be a cold/broken solder joint on a ground circuit for the final stage power regulator.  Instead of nuking my amp and possibly having a fire at my desk by continuing to use the amp (because without the meters I wouldn't have known), the meters helped me catch the problem immediately.  So now, instead of an $800 loss for the amp and potential untold damage to my home... I most likely will fix my amp for free.

 

Sometime we are prioritizing the wrong potential losses.

I have to say this brings up another point. When running high power at 200W, who cares about the loss of a meter inline, especially on VHF. It is a very different scenario running barefoot on UHF with an already pretty long feed line.

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