Anybody have experience with MFJ equipment?

[galois]

Rather that spend time trying to build one, I am making a decision to purchase a RF field strength meter. Does any one have experience with MFJ-801? <p>http://206.131.241.58/ubbcgi/ultimatebb ... wtopic&f=1

[Edd]

I certainly like some of their more complex equipment, but for an infinitely simple project like that, why not make it yourself. Its just a diode /or/pair (1N34, 1N60, Ge) configured into a detector circuit and then feeding a microammeter. For an example see:
http://www.alphalink.com.au/~parkerp/noapr97.htm
I remember making a similar unit with a short telescoping whip and had upgraded a bit by using a two stage darlington stage prior to the meter using two of the probably first U.S. production silicon planar xstrs back in ’59. I was using it for final pruning/tuning of a 10 Meter xmit antenna. I was taking readings up to about about a quarter mile away.
Also consult the ARRL handbook for their circuit.<p>73's de Edd
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[galois]

Thanks for the input Ed! I just got involved in Amateur Radio about a year ago, and finally broke down and took technician class exam. I am a physicist by training, and have not fooled around with practical electronics for years. Your advice is greatly appreciated!!

[Edd]

Rgr Rgr :
I see I omitted to build the unit in a metal/shielded case or you might pick up more stray emissions than you want to. I used a short salvaged FM radio ant(centered inside a rubber grommet at the top) that just barely peeped thru the case top when the ant element was in its closed up position. In this manner you would be able to attain some "psuedo" RF attenuation by protruded antenna length adjustment, while the pot is left to work on detected signal level.<p>73's de Edd
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[galois]

Yes, I had considered RF shielding kind of subconsciously regardless of the circuit design. What would you suggest if I wanted to install a band selection range (toggle switch)? Do you think there is any greater level of sensitivity and accuracy if the meter is composed of seperate sub-circuits, or should I just use a tuning cap with one board to select band ranges? I realize that more features and quality = more $$.

[Edd]

THX1138…I’m always intrigued by cryptic ID’s….yours resembles my car tag #..hi hi.<p>On the making of a TUNED FSM , I had not considered doing such , since in my particular application I was interested in a LINEAR across the band response. If I was making a variance in xmit frequency, I would be up against the variance in output from the detector imparted by the gaussian sloped response of the LC tank circuit in its front end. <p>If I had wanted to incorporate a tuned front end, I probably would have chosen a ceramic/steatite rotary band switch with its rotor picking off taps on an inductor mounted on its terminal propers periphery in conjunction with a parallel air variable cap also in very CLOSE proximity. The LC combo being installed at the front end.<p>
73’s de Edd

[cato]

IMHO most everything MFJ makes is crappola. Thats a technical term. Others may disagree, I dunno. I suggest going to a hamfest, someone will be peddling MFJ stuff. See it for yourself. If your not getting QST yet, lemme know what State your in, assuming you're in a State, and I'll tell you where the next one is.<p>3333333

[sigint33]

Geez,<p>THX1138, you can't use that name! George lucas would be furious, I was in that movie as a bald extra.<p>Oh Yeah .... .. .... .. -... -.-- .<p>[ September 11, 2003: Message edited by: sigint33 ]</p>