Will a 25-60 Mhz slug work for CB? I notice they are cheaper than the 2-30Mhz ones. I know they are in the CB range but thought something was up because of the price. Thanks 
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Bird 43 Slugs
- Thread starter jammeejoe
- Start date
actually the the 'A' slugs (25-60mhz) have the broader range.
the elemements used for bird meters are basically directional couplers. the reason the 'A' slugs cost more is because the lower you go in frequency the higher the 'coupling factor'. directional couplers for lower frequecies must be made with greater care to guarantee accurracy hence the higher price.
the elemements used for bird meters are basically directional couplers. the reason the 'A' slugs cost more is because the lower you go in frequency the higher the 'coupling factor'. directional couplers for lower frequecies must be made with greater care to guarantee accurracy hence the higher price.
it happens to the best of us
i just told a guy this morning that $400 x 8 was $1600, he didn't say a word but one of my guys here quickly corrected me.
i just told a guy this morning that $400 x 8 was $1600, he didn't say a word but one of my guys here quickly corrected me.
Hmmmmm. Uh, Richard the bandwidth for the HF slugs is wider as a proportion, from lowest to highest. Bandwidth issues are generally described as a proportion, rather than so many MHz, in my experience.
25 to 60 MHz is a range of 2.4-to-1. 50 to 125 mHz is 2.5, 100 to 250 MHz is 2.5, 200 to 500, and 400 to 1000 and so on as the letters go up from "A" to "E".
First experience with the Bird 43 was entirely 25 MHz and up, an FM 2-way tool, or so I thought. Had never seen one before getting hired by the local Motorola shop. Had no idea it would cover below 25 MHz until a few years later.
But 2 MHz to 30 is a fifteen-to-one bandwidth. Always figured the "H" elements were higher because it's just tougher to flatten the frequency response over a 15-to-1 band than a 2.5-to-one band.
Folks for years have asked why the built-in "relative" RF meter in ham HF transceivers and linears always has a knob to set the sensitivity. Sometimes it's on the front panel, usually on the rear. I explain that eliminating that control would cost a bundle. A 'relative' RF meter function is cheap to build into the radio. A broadbanded wattmeter is not.
And then there were the "Firebird" and "Black Cat" wattmeters. Used to get a reaction from CB operators by patching my 3-Watt 2 meter HT into a Black Cat 2000-Watt meter, on a dummy load. When they saw a reading of around 400 Watts, I'd hear things like "I gotta get me one of these". Until I explained that it really was only three Watts. On the Bird, with the "C" slug.
Got a real appreciation for the engineering inside those "slugs" first time I tried to build a RF wattmeter from scratch, and level the frequency response. Not as easy as it sounds.
73
25 to 60 MHz is a range of 2.4-to-1. 50 to 125 mHz is 2.5, 100 to 250 MHz is 2.5, 200 to 500, and 400 to 1000 and so on as the letters go up from "A" to "E".
First experience with the Bird 43 was entirely 25 MHz and up, an FM 2-way tool, or so I thought. Had never seen one before getting hired by the local Motorola shop. Had no idea it would cover below 25 MHz until a few years later.
But 2 MHz to 30 is a fifteen-to-one bandwidth. Always figured the "H" elements were higher because it's just tougher to flatten the frequency response over a 15-to-1 band than a 2.5-to-one band.
Folks for years have asked why the built-in "relative" RF meter in ham HF transceivers and linears always has a knob to set the sensitivity. Sometimes it's on the front panel, usually on the rear. I explain that eliminating that control would cost a bundle. A 'relative' RF meter function is cheap to build into the radio. A broadbanded wattmeter is not.
And then there were the "Firebird" and "Black Cat" wattmeters. Used to get a reaction from CB operators by patching my 3-Watt 2 meter HT into a Black Cat 2000-Watt meter, on a dummy load. When they saw a reading of around 400 Watts, I'd hear things like "I gotta get me one of these". Until I explained that it really was only three Watts. On the Bird, with the "C" slug.
Got a real appreciation for the engineering inside those "slugs" first time I tried to build a RF wattmeter from scratch, and level the frequency response. Not as easy as it sounds.
73
edit, retraction
i still agree with nomad but im confused :? , i just tested this with several meters and they do different things some under read and some over read, i always thought they all over read when used higher than their rated frequency like nomads ht on the black cat but some meters do one thing and some another, the bird 25-60 slug reads way lower than the 200-400mhz slug when used on vhf/uhf, kenwood underreads both below and above its rated frequency, tellewave undereads below its rated range but comes with a compensation chart, some cheap cb meters show high power at vhf/uhf and one shows virtually nothing at uhf, i need to check all my meters and look what kind of couplers they use to try and figure whats going on :roll: ,
i also thought richard meant you need more coupling at lower frequencies
i still agree with nomad but im confused :? , i just tested this with several meters and they do different things some under read and some over read, i always thought they all over read when used higher than their rated frequency like nomads ht on the black cat but some meters do one thing and some another, the bird 25-60 slug reads way lower than the 200-400mhz slug when used on vhf/uhf, kenwood underreads both below and above its rated frequency, tellewave undereads below its rated range but comes with a compensation chart, some cheap cb meters show high power at vhf/uhf and one shows virtually nothing at uhf, i need to check all my meters and look what kind of couplers they use to try and figure whats going on :roll: ,
i also thought richard meant you need more coupling at lower frequencies
nomadradio said:
you are exactly right, but moleculo was not refering to bandwidth as a ratio but as a frequency spread. i didn't realize that my reply to him was making it sound as if i didn't understand what was going on with these units, bandwidth, Q, etc. i was only stating that his thinking was off (and leaving it a simple one line reply so he would not think i was calling him a dumb a$$). the 2nd part of my post was directed at an explanation. which leads me on to my next part......
your second paragraph that i c/p'ed above is a very simple and understandable way to explain what i was trying to say about these meters. it is much easier for someone to picture what you are saying with the ratios than where i was going with directional couplers. most do not know what a directional coupler is and going into great detail would probably have confused more people than it would have helped (my experience from doing long and in depth posts in the past). that is why i left it at the fact that designing a directional coupler to work over a wide range of low frequencies is much more difficult than designing one to work over a wide range of higher frequencies.
Whew... That's a relief. You had me worried for, maybe a few milliseconds plus or minus.
Saying something technical in a way that's brief enough they can stay awake all the way through counts for a lot. If it puts them to sleep or loses them in jargon, the time spent writing it was wasted.
Lord knows, transmission-line math still gives me a headache. Thank goodness for nomographs, conversion charts and calculators. Much better someone else works that stuff out so I can just copy what I may need.
I appreciate the effort involved in boiling things down for an audience of non-engineers. Hope I didn't make it sound as though I don't.
73
Saying something technical in a way that's brief enough they can stay awake all the way through counts for a lot. If it puts them to sleep or loses them in jargon, the time spent writing it was wasted.
Lord knows, transmission-line math still gives me a headache. Thank goodness for nomographs, conversion charts and calculators. Much better someone else works that stuff out so I can just copy what I may need.
I appreciate the effort involved in boiling things down for an audience of non-engineers. Hope I didn't make it sound as though I don't.
73