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Killer
New member
Username: Killer
Post Number: 5
Registered: 1-2007
| | Posted on Sunday, April 01, 2007 - 10:09 am: | 
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OK heres the deal.I have a MFJ 259B analyzer ordered.This will be the first one I've ever used so i may need a little help with it.
1st question.Do i need to hook it up the the antenna with the same piece of coax that will be used to connect the antenna to my radio?the reason i ask this is because my coax running from the house the the antenna will be close to 175 feet long.Will this long run affect the meters reading.Our do i just need to use a short piece of coax to set the antenna?
Next question.After i have my antenna tuned for low SWR's with the analyzer how do i check my SWR's with every thing in line.I do have a regular swr meter but if my antenna is tuned right but after every thing(amp included) is in line and turned on,do i still need to believe my in line meter if it reads different than the analyzer did?
Thanks in advance for for any help. |
Patzerozero
Senior Member
Username: Patzerozero
Post Number: 3576
Registered: 7-2004
| | Posted on Sunday, April 01, 2007 - 11:19 am: |
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killer, read the instructions CAREFULLY that come with your 259b. you can check if your 175 foot piece of coax is good, & how much line loss you have. (the 259b should show you about 1.8db of loss through 175' of 213 cable-the lowest quality you should use at that length-because 175' of 213 with 1.1:1 swr @ 27.205 mHz will be roughly 30-35% signal attentuation, or, a 100 watt signal will only put about 65 watts out at the antenna).
yes, take the SHORTEST piece of coax you can to adjust the antenna, a couple feet if possible, 1st to the freq you want it resonant on, then to as close to 1:1 impedance match you can get. without having to run back & forth 175' to the radio after adjustments.
if you'd like, you can check all of your jumpers with the 259b, too. once the antenna is tuned,put everything together, check SWR, if you see MAJOR differences between amp on/amp off, try changing lengths of jumpers 1st, placement of cables & station grounds. the 259b will show problems through the entire line, you just need to know where to start changing things. o poorly matched amp (a possiblity) will make things tough to match. NEVER key the radio with the 259b in line, or you'll be buying another. |
Tech833
Moderator
Username: Tech833
Post Number: 1638
Registered: 8-2002
| | Posted on Sunday, April 01, 2007 - 12:02 pm: |
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Pat is right on everything above.
Once you begin using the 259B, you will wonder how you ever got along without it.
Once you tune an antenna using the ohms and j readings the 259 gives you, you will begin to really understand what your antenna is doing and how it does it. |
Killer
New member
Username: Killer
Post Number: 6
Registered: 1-2007
| | Posted on Sunday, April 01, 2007 - 12:51 pm: |
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Thanks guys.As for my coax,i have a 500 foot roll CA-400 setting in the floor ready to go.I'll be running 2 runs of it to my SE Lightning 4+.Each run being around 175 feet and one run to my ground plane which will be around 70 feet long. |
Hollowpoint445
Senior Member
Username: Hollowpoint445
Post Number: 1471
Registered: 6-2004
| | Posted on Sunday, April 01, 2007 - 5:40 pm: |
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I'd use a short piece of coax to adjust the antenna, and then after installing the main run I'd check it again because the additional coax length might make the antenna work a little differently and some adjustment might be in order.
I'd suggest the same if you're adjusting the antenna match while it's close to the ground, and later moving it into position.
I agree with Tech833 - I don't know how I ever got along without my 259. I don't think I'll ever use all of it's capabilites, but it'll be fun to try.
Get yourself rechargeable batteries, because everyone you know will be borrowing it when you're finished with your installation.
Aack! - Bill the cat
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Patzerozero
Senior Member
Username: Patzerozero
Post Number: 3581
Registered: 7-2004
| | Posted on Sunday, April 01, 2007 - 5:25 pm: |
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good deal on the 400 cable, killer. lmr400 spec's at about 22-23% loss in the situation i noted above. a 100 watt signal will get about 77 watts to the antenna! |
Tech833
Moderator
Username: Tech833
Post Number: 1640
Registered: 8-2002
| | Posted on Monday, April 02, 2007 - 10:24 am: |
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Don't forget- Coax loss works 2 ways. If your 100 watt radio loses 23 watts when transmitting, big deal. But, what if you have a signal hitting your antenna with only 10 uV? Then, a mere 7 uV gets to your radio and a readable signal is suddenly in the noise? THAT is the most important cable loss consideration. When you consider transmit loss, it doesn't seem so bad, but you have to hear someone if you are going to communicate with them. Receive loss is what really matters.
In your situation, I agree that the LMR-like cable is an O.K. choice for 150 foot runs. I would prefer 1/2" Heliax for a run that long if it were me. |
Killer
New member
Username: Killer
Post Number: 7
Registered: 1-2007
| | Posted on Monday, April 02, 2007 - 6:35 pm: |
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I agree Tech833 about the 1/2" Heliax but I'm on a budget as it is.I'm trying to put up the best station i can afford with "afford" being the key word.Do you think a per amp would help or just magnify the noise so much that its a waste of money. |
Patzerozero
Senior Member
Username: Patzerozero
Post Number: 3586
Registered: 7-2004
| | Posted on Monday, April 02, 2007 - 11:34 pm: |
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if you can find a gaasfet-tpye preamp that will cover the band you're using-cb i guess-then i'd say 'maybe'. the standard cb-type preamp, such as in a linear or the maco preamp, they just magnify the noise with any signal. |
Tech833
Moderator
Username: Tech833
Post Number: 1642
Registered: 8-2002
| | Posted on Tuesday, April 03, 2007 - 2:33 pm: |
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Pat is right (again!).
If your budget is a consideration, then use what you have. But save up for some upgrades in the future. And, of course, please remember to report back and tell us how it works! |
Killer
New member
Username: Killer
Post Number: 9
Registered: 1-2007
| | Posted on Tuesday, April 03, 2007 - 6:11 pm: |
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I cant seam to find a gaasfet preamp for the 11 meter band.Most of what I'm finding is for SSB operation and a few for the ham bands.Do they make them for 11 meter?
Thanks for the help guys.And yes i will let you know how well it all works. |
Patzerozero
Senior Member
Username: Patzerozero
Post Number: 3593
Registered: 7-2004
| | Posted on Saturday, April 07, 2007 - 2:58 pm: |
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thank you, paul 
heliax will get you back another 10 watts, up to around 87 out, based on the earlier scenario!
ICE products(i think) used to make them for transmitting-broadbanded & individual bands including 11m. looking at their site, i guess they only make them for RCV now. i have an older AMECO broadbanded preamp, that i don't use, because it seems to work based on the noises in the air. if it is EXCEPTIONALLY quiet, then it seems to increase the readability of a distant station, if there is ANY noise, forget it, the signal increases with the noise. so, i don't even have it in line-why risk ANY additional rcv or xmit losses with something needlessly in line?
with your 4 element quad, at least 400-type coax & a decent receiver, you will NOT need to worry about a preamp! you'll find yourself turning the RF gain to ATTENUATE things you DON'T want to hear! |
Killer
Junior Member
Username: Killer
Post Number: 10
Registered: 1-2007
| | Posted on Wednesday, April 11, 2007 - 9:58 pm: |
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My MFJ 259B arrived today :-) |
Bruce
Senior Member
Username: Bruce
Post Number: 4416
Registered: 9-2003
| | Posted on Thursday, April 12, 2007 - 6:34 am: |
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The MFJ preamps will go on 11 meters
On 6 since 66
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Killer
Junior Member
Username: Killer
Post Number: 12
Registered: 1-2007
| | Posted on Monday, April 16, 2007 - 8:30 pm: |
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One word describes my new MFJ 259B....Awesome!!
I used it today to setup the antenna on my mobile.Turns out what i thought was a well tuned antenna was actually way off.My antenna was preforming in the 25Mhz range better than 27Mhz.I originally set it up with my Para-dynamics SWR/power meter.When the SWR meter said 1.5 my analyzer said 3.1.Thats right a 3.1.And i been running my amp this way.luckily nothing has been damaged to the best of my knowledge.Now that i have the antenna tuned the right way i can tell a big difference on my receive.It always did seam to get out fine but my ears are improved at least 25%.Now i got to tune my Lighting 4+ and mt Imax 2000 when I'm ready to put them up.
I'm still new to the analyzer so i got a lot to learn about all the things it can do but as far as setting SWR's goes,it's a breeze to use.I know they are a little on the expensive side but its well worth the money.I cant see myself setting up another antenna with out it . |
Drzuo
Junior Member
Username: Drzuo
Post Number: 10
Registered: 1-2006
| | Posted on Sunday, May 20, 2007 - 2:04 am: |
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With your antenna analyzer, set your antenna so x=0 at the desired center frequency. Hook it up to your antenna using a short jumper, but be careful not to be so close that you effect the signal. One you get x to equal zero your antenna is resonant. The swr may not be at it's lowest at resonance, this is ok. Once you introduce your normal longer coax back into the system your swr should drop due to ground loss. |
Tech237
Moderator
Username: Tech237
Post Number: 789
Registered: 4-2004
| | Posted on Sunday, May 20, 2007 - 7:15 pm: |
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"Once you introduce your normal longer coax back into the system your swr should drop due to ground loss." - that is NOT OK. This does not mean that the SWR is lower just that there is sufficient loss in the cable to show an apparent drop in SWR due to the lower power level coming back.
This is one reason I always advocate "test the antenna as close as possible to the conditions it will be run under" If you need 100ft of coax setup the antenna using that 100ft of coax otherwise any readings you get basically inaccurate.
Simon
Tech237
KD7IEB
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Drzuo
Junior Member
Username: Drzuo
Post Number: 11
Registered: 1-2006
| | Posted on Thursday, May 24, 2007 - 7:57 pm: |
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Tech, if you add coax, the resistance of the coax will make the swr appear to drop-that's just physics. You aren't tuning for lowest possible swr, ( although the swr is generally low around resonance)you should be tuning for resonance. Antennas with an unusually low swr over a wide frequency range is usually the result of a lot of ground loss, and will probably radiate like ••••. Antennas with great grounds will usually exibit a higher swr, or at least a narrower, sharper curve. You want to measure the resonance of the antenna so you should measure at the antenna.( or as close as possible) If your coax is radiating, try a 1:1 balun. |
