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VHF/UHF SWR/Wattmeters

Discussion in 'Amateur Radio News' started by WJ6F, Dec 10, 2020.

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  1. KG7HVR

    KG7HVR Ham Member QRZ Page

    I dont trust most do all meters. Its very hard to do accurately. The meter on vhf and hf is a compromise usually without expensive circuits. And pep reading meters dont use caps for hang time. If it works without external power its not true pep reading.
    I wont attack mfj. They are a ok reference point.
    I use a older 989c tuner and the meter is decent but never quite agrees with my many radios. Its close.
    I think specific meters for specific bands is better. No matter the brand. And you wouldnt wanna change jumpers to go to a uhf to hf or vhf rig. So do all only works if you have a shack in the box like ts2000 or something.
    I think i read somewhere bird is only 15% accurate? But people sure swear by them.
    Maybe the lp100 by telpost is the ticket?
    This is a good topic for sure.
    K4FMH likes this.
  2. KG7HVR

    KG7HVR Ham Member QRZ Page

    Truth hurts when they call you like it is.
    G7DAZ and K4FMH like this.
  3. W3PX

    W3PX Ham Member QRZ Page

    The Bird sensing element, or slug, is calibrated at the factory via an internal potentiometer. This calibration is necessary due to variables including the detector diode's characteristics and manufacturing tolerances.

    Long term measurement accuracy can change due to component aging. Over the short term, accuracy can vary due to temperature.

    The accuracy of Bird wattmeter elements is specified as +/- 5% of the full scale reading. So, If you are using a 250W element to measure a 100W RF source, the reading you get could vary between 87.5W to 112.5W and still meet specs.

    Even when using an element that is well matched to the power level being measured, the uncertainty band of 10% (+/-5%) is fairly broad. Small deviations in calibration accuracy due to temperature and component drift could easily fit within this window, but that does not mean the accuracy of the instrument won't degrade over time.

    Here's an interesting article by WA1MIK that details the internal construction of a Bird element:

    73 Frank W3PX
    KG7HVR likes this.
  4. K4YNZ

    K4YNZ XML Subscriber QRZ Page

    "I never calibrated a bird." why? When I worked at GTE the calibration truck would come to the office and stay a week. They would go through all our Bird slugs. They are adjustable. They do age. Drilled a little hole in the cover. Put a sticker over the hole. Used Bird for AMPS Cellular. HP for digital and microwave. Bird is a great meter when used correctly. I still have a couple. But my Telepost LP-100 is more accurate and will do more. For most + or _ 10% is ok. The Drake W4 I bought as a Novice still works great. Still very accurate when compared to other meters. I used to figure current and voltage to get input power to check if my meter was in the ball park.
    Everyone has a favorite meter. At work I liked a combined HP Frequency counter and power meter. You adjusted your frequency. Saved it as your calibration factor and adjusted power. No charts to lose at 2 AM when your are trying to replace a LO and want to get home.
  5. K2XT

    K2XT Premium Subscriber QRZ Page

    Yes it is, good topic.
    Bird is +/- 5% of full scale as others have mentioned.
    LP100a specs say 5% also, but are calibrated to 3% traceable to NIST, presumably at any frequency since there is no "full scale" meaning in a digital instrument.
    Maybe a slug is calibrated to better than 5% initially also?

    I thought maybe a spectrum analyzer is the answer. Checked the Siglent specs on the $1500 model. It is 0.7 db which is about 15%. So much for that idea.
  6. KC5HWB

    KC5HWB Ham Member QRZ Page

    "Truth" on QRZ is subjective only to the poster of the statement, no matter how little research they do. Similar to what you just did.
    KD5BVX likes this.
  7. KG7HVR

    KG7HVR Ham Member QRZ Page

    Lol 15% yeah. And $1500
    I sure could use a good vhf meter. I have some old mirage 160w amps that people claim do 300w
    K2XT likes this.
  8. KG7HVR

    KG7HVR Ham Member QRZ Page

    Then why do you need to post on qrz? If your so amazing you should be able to stand alone. Instead you and you boys flood use with content. Content doesn't always mean quality. Maybe it was ok when it was just you but now theres a ton of copy cats. Who want fame, free stuff, attention, $ money , whatever. In the end it has a negative impact. Your here to help yourself first and foremost. Im sure youve helped many people but its not amusing anymore. And i know your buddy buddy with qrz people because they always protect you. So anyway if you have a bunch of people telling you the same thing maybe its time to look at your behavior and actions and try and see how its getting you this attention that you dont like. I think your a smart guy so figure it out.
    N1IPU likes this.
  9. KC5HWB

    KC5HWB Ham Member QRZ Page

    The basic answer to your first question is that I want to provide a positive influence on QRZ. Comments like yours that you and others make can't be the norm for other folks coming onto this forum, for an example of how Hams treat each other. We need to have a positive light and example to others. I try to help people - and I get bashed for it, like you just did. But if I stop now, that means you win, right? And your attitude doesn't represent the Amateur Radio that I have been involved in for the past 25 years.

    I won't reply here again, send me an email if you want to discuss. I don't think taking over Craig's post is the place to talk about this.
    KD5BVX and K5ATA like this.
  10. KD5BVX

    KD5BVX Premium Subscriber QRZ Page

    I see a trend and that is that some seem to be jealous of certain others who have YouTube channels or websites so they resort to insults and negativity. Keep up the good work and positive attitude, everyone. I appreciate the mods and admins here who not only want you all to share your videos here (which I now you all don't share all of your videos here, regardless of what some claim) but also help keep these threads a little cleaner by deleting negativity and attacks toward any of you. We should all be more supportive of each other, especially of those who are working to continue to promote and support the amateur radio hobby.
    KC5HWB likes this.

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