It should be antenna coax to meter, meter to amp and amp to radio.
Or, put another way, you transmit from the radio into the amp. The amplified signal now travels from the amp to the meter and from the meter to the antenna.
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Cobra 18 WX ST II (don’t laugh)
- Thread starter ForestRunner98
- Start date
It should be antenna coax to meter, meter to amp and amp to radio.
Or, put another way, you transmit from the radio into the amp. The amplified signal now travels from the amp to the meter and from the meter to the antenna.
Can’t measure your amp output unless the meter is between the amp and the antenna.
I check swr by taking the amp out of line and place swr meter in place. Making sure antenna is tuned, then put linear back in.
Can’t measure your amp output unless the meter is between the amp and the antenna.
That makes sense! I switched the cables around so the meter is between amp and antenna. Spitting out 80 watts.
Well, now with the meter between the amp and antenna I am seeing SWR at 1.5 across all channels with the amp “off”. Amp “on”...it shoots up on ch1 and 40 to 2.5 and at ch19 it’s at 1.8
It’s the opposite effect I had before the switcheroo. Seems like the more common issues with an amp.
In a way , yes it is what I'm referring to - and why Coax length problems show up - transmutation of one impedance to another just to tighten the mismatch using coax as your balun...not the best idea...
Your situation is not unique - in that it happens amongst the configurations of various amps and the types of networks the radios and amps use - not always the most compatible or leak-proof bullet-proof designs either...
I wish I knew really what to tell you - but answers I get even from the former techs I worked with can only say that the layouts are different...work accordingly
Like this ...
Galaxy 939
Galaxy 88
One was a throwback to Biupolar and the other is the modernized MOSFET...
Network's are different is what the tech tell me - the newer lines and layouts of these models are not neutralized like they were in the older days.
Yes it was like that. Now it’s radio, amp, meter, antenna.
I was able to get the SWR down to 2 with the amp on. Amp off and the SWR’s are 1.3 - 1.5
@ForestRunner98 - at the risk of getting flamed (again - by others) ... I'll try and give you some advice about this so you can then use it to help make choices.
Right now, with you "retuning" the antenna to the AMP versus straight thru to the radio with that amp in BYPASS mode, you are seeing a "bump" in the impedance that many talk about as mis-match...
Well, yes it is, and is why the issue of how to make everything equal - is just not as simple as tuning the antenna anymore...
You have two choices,
One, tune for lowest SWR for the moments you need the low-SWR protection when you run your equipment in a MUST HAVE EVERYTHING HARD OVER FULL ON NO STOP ALL THE WAY UP situations.
... or ...
Just run your equipment as if you can toggle on or off your in-line stuff as you need and not have to worry so much about SWR because "I'm not pushing the equipment to it's limits" so therefore I run my equipment in my own level of performance and I am ok with it.
Ok, with the above being said, not many people can find good techs that will offer to help you smooth out this impedance bump. Instead, you will find techs that - unfortunately - they'll try to sell you Snake-Oil and SWR-Spray along with a "special jumper cable" that can fix your problems, whiten your teeth and get you to the Front OF The Line at the local American Idol Audition...
With the issue of most Amps "mass made" these days and most are imports, the ability to locate the exact components to swap out - let alone obtain the proper sized and configured ones to replace it - is a crap shoot. So if you can read a schematic and locate the output ferrite cores and are willing to take on the impedance bump problems yourself, good luck. It helps to keep us in your loop and have a neighbor that came from the SAME country the amp was made in, offering to help you decipher their language barrier - as well as locate a supplier that speaks that same language - you may be in luck...
In the older days, we just used to locate the input caps and output networks and their caps and make some tweaks and view the results - gone too far? re-do and go in the OTHER direction as far as parts values go. It's RF and you're looking for 50-ohm - not necessarily a Hi-Cut or even a Low-Pass filter to keep the Harmonics down - you just want to make the thing work like a 50 ohm system the regular radio without all this extra stuff - did before.
So again looking at the newer stuff arriving on our shores, you're left with few choices let alone options. You want it to work, Then TUNE for the best averages and drive the system at it maximum level you're comfortable with and hope the Mean Time Between Failures is not within your lifetime...
Right now, with you "retuning" the antenna to the AMP versus straight thru to the radio with that amp in BYPASS mode, you are seeing a "bump" in the impedance that many talk about as mis-match...
Well, yes it is, and is why the issue of how to make everything equal - is just not as simple as tuning the antenna anymore...
You have two choices,
One, tune for lowest SWR for the moments you need the low-SWR protection when you run your equipment in a MUST HAVE EVERYTHING HARD OVER FULL ON NO STOP ALL THE WAY UP situations.
... or ...
Just run your equipment as if you can toggle on or off your in-line stuff as you need and not have to worry so much about SWR because "I'm not pushing the equipment to it's limits" so therefore I run my equipment in my own level of performance and I am ok with it.
Ok, with the above being said, not many people can find good techs that will offer to help you smooth out this impedance bump. Instead, you will find techs that - unfortunately - they'll try to sell you Snake-Oil and SWR-Spray along with a "special jumper cable" that can fix your problems, whiten your teeth and get you to the Front OF The Line at the local American Idol Audition...
- Sigh - yeah.. right...There is some truth to this - but the term is BALUN, as in, "I've got little choice but to do it this way to make this Hi-Po Miracle of my System to Work Right..."
With the issue of most Amps "mass made" these days and most are imports, the ability to locate the exact components to swap out - let alone obtain the proper sized and configured ones to replace it - is a crap shoot. So if you can read a schematic and locate the output ferrite cores and are willing to take on the impedance bump problems yourself, good luck. It helps to keep us in your loop and have a neighbor that came from the SAME country the amp was made in, offering to help you decipher their language barrier - as well as locate a supplier that speaks that same language - you may be in luck...
In the older days, we just used to locate the input caps and output networks and their caps and make some tweaks and view the results - gone too far? re-do and go in the OTHER direction as far as parts values go. It's RF and you're looking for 50-ohm - not necessarily a Hi-Cut or even a Low-Pass filter to keep the Harmonics down - you just want to make the thing work like a 50 ohm system the regular radio without all this extra stuff - did before.
- Before Flames erupt -t's important to mention that Spectral Purity and Amplifiers are contradictions in terms to themselves.
- There are events that occur and devices you can use, that others have mentioned that are expensive options for those whom only want to be casual - not a casualty of bankruptcy due to the support and necessary equipment needed to obtain as well as maintain this Low - SWR as well as no spurries.
- You already have the biggest indicator and tools to show you have this problem - to fix it requires a known reference and a direction.
- IF you were to put this on a dummy load, you'd see all the power in the system going into a BROADBANDED LOAD device that will accept any and all power into itself and not show any output problems. Using a device like a Spectrum Analyzer will also show these spurries that your SWR won't.
- It' is when you install this in your vehicle and the whole mess is out of whack - your best indicator is your SWR meter, your best tool to detect them is your antenna.
- How? By the ability to tune to a KNOWN 50 ohm REACTIVE impedance - you get low SWR when you just use the radio to antenna. Now when you install the amp the SWR is different - the amp in-line is a bump - you have to figure out the impedance of this bump as well as the increase in power that goes to the antenna may contain Spurries that ADD a REACTIVE impedance reflection BACK to your SWR meter and radio.
- Spurries are RF power signals above and around the frequency of your system but not in the BAND your using the antenna in. So they are HARMONICS of your initial RF frequency
- Letting LOGIC take over, your antenna is tuned for your CB band - 27MHz. But if spurries are extra frequencies you can call these frequencies Harmonics, you can see this power as a signal in the 52MHz range and above - your Antenna is NOT tuned for that - so this power is reflected back and added as your SWR reading.
- Your antenna looks like a 50 ohm load at 27MHz (for example) and if you produce a lot of power that goes into other frequencies outside the 27MHz band, that power going to the antenna make it look like something a lot different - like closer to a 1/2 wave end fed radiator versus a 1/4 wave ground plane.
- The former, a1/2 wave end-fed antenna is a lot different and higher impedance than a 1/4 Wave ground plane.
- Simply put, your REACTIVE load, the antenna - is the best indicator of your SWR problem but to solve this correctly you'll need more tools that are expensive to own and require experience to use and even more knowledge to interpret the results and provide direction to fix these issues.
- You have two problems you need to see if you can even fix let alone work with.
- Harmonics or Spurries produced by excessive power or poorly designed equipment...
- Impedance mis-match because the system is not truly 50 ohm all the way down the line.
So again looking at the newer stuff arriving on our shores, you're left with few choices let alone options. You want it to work, Then TUNE for the best averages and drive the system at it maximum level you're comfortable with and hope the Mean Time Between Failures is not within your lifetime...
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Watch out for spurious at 81-82 MHz too. That won't be reflected, but it will be radiated because your 1/4 wave antenna will be an odd multiple of 1/4 waves again, hence low impedance.
Shadetree Mechanic
Delaware Base Station 808
A low pass filter would help. I run a big one in my shack. Here is a little one.
http://www.rmitaly.us/index.php?main_page=product_info&products_id=144
http://www.rmitaly.us/index.php?main_page=product_info&products_id=144
Shadetree Mechanic
Delaware Base Station 808
@Handy Andy
I will take all that advice! At this point I will run it when I need the extra push. I have a longer 4ft antenna that I will try and see what those numbers are. I also looking into better coax. I will start with the jumpers. This is a brand I am looking at:
From what I read this brand is good. If not please say so.
thanks!!!
I will take all that advice! At this point I will run it when I need the extra push. I have a longer 4ft antenna that I will try and see what those numbers are. I also looking into better coax. I will start with the jumpers. This is a brand I am looking at:
From what I read this brand is good. If not please say so.
thanks!!!
@ForestRunner98 - keep going - you're doing fine...
But ask yourself this, do I need to have the best coax money can buy, or the best coax for the job - that decision is up to you. Spending more than you need to is not always the most effective option. What you need to look at is the small stuff you'll have to live with once you get this off the ground...
Simple stuff like.
) depending on the demands of the system - it's your system - run it the best way you know how - we're only here to help you obtain that - not misguide you. If I send you the wrong way, you may get frustrated or otherwise disappointed - that's not my intent with this help I'm trying to supply you.
Remember to look thru your orders and even do a Google search on the brands you wish to try - take the reviews as they are, just Reviews, Done by humans looking for a particular type of performance to cost effectiveness or more hits to their site for monetary gain.
You'll see - some will praise, others will hate - and some will actually be good enough for you to use to help make up your own mind. But the best advice; is to remember you're dealing with "losses" in the different jumper lengths and your impedance bump of an Amp may add SWR problems to this, or - with the right coax, take it away by lessening it's effects and allow reliability to take over. (Your whole issue may be a bad section of coax - that can be easily fixed with the right coax for the job)
We can't fix some stuff, but if you can improve the portions of the system you can, every little bit helps - especially with the types of coax out there. To put it succinctly - some coax out there is much like a piece of damp string - you may be better off just putting a dummy load on the back of the amp and run it that way....
You may need to brush up on making your own patch cord coax, meaning you may need to learn how to install connectors on your coax for the best length to losses ratios. There are a lot of users out here, and out there, to help you with that, but - for best results - you have to do the work. Best lesson's are learned thru direct experience.
But ask yourself this, do I need to have the best coax money can buy, or the best coax for the job - that decision is up to you. Spending more than you need to is not always the most effective option. What you need to look at is the small stuff you'll have to live with once you get this off the ground...
Simple stuff like.
- Dielectric
- Braid shielding
- Type of Conductor
- Sleeve or Jacket material used
- Flexibility
- turn radius without collapsing
- Diameter
) depending on the demands of the system - it's your system - run it the best way you know how - we're only here to help you obtain that - not misguide you. If I send you the wrong way, you may get frustrated or otherwise disappointed - that's not my intent with this help I'm trying to supply you.Remember to look thru your orders and even do a Google search on the brands you wish to try - take the reviews as they are, just Reviews, Done by humans looking for a particular type of performance to cost effectiveness or more hits to their site for monetary gain.
You'll see - some will praise, others will hate - and some will actually be good enough for you to use to help make up your own mind. But the best advice; is to remember you're dealing with "losses" in the different jumper lengths and your impedance bump of an Amp may add SWR problems to this, or - with the right coax, take it away by lessening it's effects and allow reliability to take over. (Your whole issue may be a bad section of coax - that can be easily fixed with the right coax for the job)
We can't fix some stuff, but if you can improve the portions of the system you can, every little bit helps - especially with the types of coax out there. To put it succinctly - some coax out there is much like a piece of damp string - you may be better off just putting a dummy load on the back of the amp and run it that way....
You may need to brush up on making your own patch cord coax, meaning you may need to learn how to install connectors on your coax for the best length to losses ratios. There are a lot of users out here, and out there, to help you with that, but - for best results - you have to do the work. Best lesson's are learned thru direct experience.
Andy's spot on. You have to access what is needed and what is wanted. Notice his point about bonding? That 240 is great, but look at velocity factor. 8U used to be the big dog. I use BuryFlex, only because I have plenty. It's stiff, tough, and direct burial. Not that you need the overkill. Turning radius is long. JEFA has some 400 I wish I had seen before ordering more BuryFlex.
If you can half ass solder, install the coax pl-259 yourself. Amphenol is the best. But use your judgement and cost effectiveness. Most of all use the K.I.S.S. Method- keep it simple stupid.
If you can half ass solder, install the coax pl-259 yourself. Amphenol is the best. But use your judgement and cost effectiveness. Most of all use the K.I.S.S. Method- keep it simple stupid.