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VERNONOTT
| | Posted on Wednesday, June 06, 2001 - 10:30 am: | 
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307 : I've been looking at one of these analyzers which has a freq counter ,rf signal generator,swr analyzer,rf resistance and reactance analyzer,coax analyzer, capacitance and inductance meters and digital read out .It appears that you do all the checks from the coax through the antenna without the need to have the radio connected.It's under $300.00 and if I thought I could figure out how to use all the features I would buy it in a flash.Are you familiar with this equipment? |
307 (307)
| | Posted on Wednesday, June 06, 2001 - 1:06 pm: |
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Fortunatly I can answer this one to a "T". The MFJ you are reffering to is really good for a ball park measurement. The Frequency Counter as well as the RF Signal Generator are NOT Phase Lock Looped and run off of an unstable ocillator with a multiplier function to have massive bandwith and cover a large frequency span. They are not even close to being accurate. A typical signal at 27.215 will have a plus or minus of about 10 Mhz. They are great for quick Antenna work though because the antenna does not care and averaging is all that is needed. And yes you do not need a radio hooked up. Save your money and by a BIRD. |
Anonymous
| | Posted on Wednesday, June 06, 2001 - 1:28 pm: |
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307 did you mean 10khz off (not 10mhz)? |
Anonymous
| | Posted on Wednesday, June 06, 2001 - 1:19 pm: |
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MFJ = Mighty Fine Junk.... |
307 (307)
| | Posted on Wednesday, June 06, 2001 - 6:55 pm: |
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No , I meant "10 MHZ" ( MEGAHERTZ)!!!! Not KHZ!!!! |
anonymous tech
| | Posted on Wednesday, June 06, 2001 - 11:45 pm: |
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i find this hard to believe. i work as a bench tech with business band radios everyday. many are xtal controlled. i have never seen any xtal controlled device that has had a +or- 10mhz (20mhz all together) freq error, even after an 8 to 9 time multiplication (uhf). we are talking hf here, so that is even more unbelievable.
the few times i have used the 259 it worked great. i once tested one against a $17,000 motorola service monitor for accuracy on the freq end. it was only about +2khz off on both generation and for counting in the highband vhf area (150mhz). at 30mhz it was only about .7khz off. i guess we need to have that service monitor recalibrated. i've been sending out radios that were +- 10mhz off.
as for the antenna not caring, i do not know of one 11meter antenna that likes to see 17mhz or 37mhz (10mhz error) going into it. that is the same as keying 17 or 37mhz into it, only at a very low level. |
307 (307)
| | Posted on Thursday, June 07, 2001 - 6:18 am: |
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That is not really what I am talking about. I also have some nice equipment and I am saying is that the linearity of the sweep is not all that accurate. If you have one of these units , try to put it on an exact frequency sometime (not the counter) but the generator , you will see that if you so much as touch the "tune" knob it jumps as much as 10 Mhz. Mine does , however maybe mine is bad....Point is , buy a BIRD..... |
vernonott
| | Posted on Thursday, June 07, 2001 - 6:44 am: |
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Too late now.In between the time I asked the question and the time I got your answer ( which was fairly quick ) I had already called the order in and it should be delivered today.Mr. Bird will have to wait until next time. |
vernonott
| | Posted on Friday, June 08, 2001 - 9:29 pm: |
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307 : I received the MFJ today and took some readings that I don't fully understand.Maybe you can shed some light on the subject.I'll make a chart showing what readings I took.Also how does my antenna system look?
Frequency---SWR----OMHS-----Coax Loss
26.965-------1.1------47--------10 db
27.105-------1.2------52--------12 db
27.205-------1.2------48--------9.5 db
27.405-------1.3------42--------8.6 db
Why does the coax ohms change so drastically? |
307 (307)
| | Posted on Friday, June 08, 2001 - 9:33 pm: |
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It depends , how long is the antenna coax? |
vernonott
| | Posted on Saturday, June 09, 2001 - 11:45 am: |
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Newsflash : Old Dog learns new trick.After seeing the sad shape my mobile antenna setup was in and has been in for two years, I hooked up the new MFJ and started cutting off one eighth inch of mass at the time.At the sweet spot of one and one eighth inch removed, coax through antenna ohms is at 52 ohms ,swr is at 1.2,and coax loss is at 9.5 db.I don't know that this is anywhere near perfect but it is a major improvement over the reading I posted here last night. |
vernonott
| | Posted on Saturday, June 09, 2001 - 9:29 am: |
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It's going to take awhile for me to understand the readings I'm getting with this new toy.I checked one of my mobile units this morning and coax ohms were 89 at 27.105,1.7 swr,5.6 coax loss.This is a Wilson 1000 roof mount antenna with factory attached coax.I'm hopeing this old dog can learn some new tricks about trouble shooting antenna systems. |
vernonott
| | Posted on Friday, June 08, 2001 - 9:45 pm: |
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Exactly 100 feet. |
vernonott
| | Posted on Saturday, June 09, 2001 - 9:48 pm: |
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307 : If you notice in my last few post,which aren't in order, on my mobile I brought the omhs down,the swr down , and in the process gained coax loss.Is that common or is there still something out of sync. |
307 (307)
| | Posted on Sunday, June 10, 2001 - 3:52 pm: |
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That is ok , you are properly matched now and the closer you are the more the accuracy will stand. I am not sure why all the loss though , at 27 Mhz , you should see hardly any...I must think on this one. |
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