| Message | Date | From | Subject | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| 12753 | 2016-04-29 12:20:42 | peter_dl8ov | UHF Power Meter Detector Diodes | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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I want to build a simple power meter to measure the output of a 70cm amplifier. Can someone suggest a suitable detector diode?
Power is 100W but this is sampled down to a more manageable level. Peter DL8OV | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| 12754 | 2016-04-29 14:02:34 | K5ESS | Re: UHF Power Meter Detector Diodes | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Peter, 12755
| 2016-04-29 14:20:32
| Phil Sittner
| Re: UHF Power Meter Detector Diodes
| Peter- I have found that several Chinese sources sell the AD8307 log amp for around $1.00 each. If you build a simple resistor divider and add an inexpensive voltmeter you'll have a very accurate and simple power meter. I have purchased the AD8307 from several of the Chinese sources and found them all to work fine. Phil KD6RM 12756
| 2016-04-29 14:23:58
| kerrypwr
| Re: UHF Power Meter Detector Diodes
| I spent some time one-finger-typing a reply but Yahoo seems to have devoured it. :(
The essence was, as Mike said, a Schottky diode; I've found that the ordinary leaded 1N5711 works fine in measuring 5 watts at 477MHz. That's the highest frequency at which I can generate "real" power and it probably works at higher frequencies. In that "lost" post I suggested a coupler to "tap" from your 100 watts but I've since realised that a ferrite coupler won't go that high in frequency; there are other ways to reduce the voltage to below the 1N5711's maximum rating. Kerry VK2TIL. 12757
| 2016-04-29 14:36:58
| kerrypwr
| Re: UHF Power Meter Detector Diodes
| My little power meter, seen here on the left;
http://s32.postimg.org/s3u4luhn9/Amplifier_Test_2.jpg uses a 1N5711; http://s32.postimg.org/hlvchziz9/Schematic.jpg
It's accurate up to at least 477MHz, which is as high as I've tested it, and SWR looks like this; http://s32.postimg.org/iqh4ymok5/SWR.jpg This seems to indicate that the 1N5711 will do your job provided, as you propose, the voltage is kept below the maximum rating of the diode. I use home-made couplers like this 30dB one; http://s32.postimg.org/6y3jivhed/Construction_Details.jpg but there are other methods. Kerry VK2TIL. 12759
| 2016-04-29 15:14:35
| DuWayne Schmidlko...
| Re: UHF Power Meter Detector Diodes
| There are a couple VHF UHF power meter projects at
http://w1ghz.org/small_proj/small_proj.htm DuWayne KV4QB 12764
| 2016-04-29 21:31:49
| Bill Carver
| Re: UHF Power Meter Detector Diodes
| Or get the Analog Devices "RF Detector Surf Board Kit" from
RichardsonRFPD. The populated board has an ADLS5902 .05-9 GHz true RMS detector, an ADL5512 .001-4 GHz 80 dB range logaithmic detector, and an ADL5511 DC-6 GHz 47 dB range Envelope/RMS detector. RIchardsonRFPD was selling the board ("ADL5XDETECTRKIT") for $5 plus shipping. W7AAZ 12765
| 2016-04-30 01:01:25
| peter_dl8ov
| Re: UHF Power Meter Detector Diodes
| Thank you for all of the replies, I just purchased some 1N5711 devices and they work quite well at 70cm.
Peter DL8OV 12772
| 2016-04-30 15:44:25
| K5ESS
| Re: UHF Power Meter Detector Diodes
| It appears the price has gone up to $10 now. Mike, K5ESS
12773
| 2016-05-01 01:30:33
| LEON HELLER
| Re: UHF Power Meter Detector Diodes
| I got two of them for $20. Shipping to the UK was a lot more. 73, Leon G1HSM 12774
| 2016-05-01 06:36:10
| Bill Carver
| Re: UHF Power Meter Detector Diodes
| Re the Analog Devices RF Detector board, I got two for $10, plus $15
shipping inside the USA. Kept one, gave one to W7OUU who's a moonbouncer/meteor scatter guy and breathes rarified GHz air regularly. W7AAZ 12778
| 2016-05-02 06:04:14
| Nick Kennedy
| Re: UHF Power Meter Detector Diodes
| I wonder if the OP was after something so exotic. I was visualizing a simple peak detector that could be calibrated in watts. I don't think I've ever seen the square law compliance of a diode used in a ham power / SWR meter. 73- Nick, WA5BDU 12783
| 2016-05-03 14:39:41
| peter_dl8ov
| Re: UHF Power Meter Detector Diodes
| Your guess was correct, all I was seeking was a relative indication of 70cm output power using a cheap edge meter. a 10 USD board would have been a massive overspend.
Peter DL8OV 12787
| 2016-05-04 00:03:19
| kerrypwr
| Re: UHF Power Meter Detector Diodes
| For interest, Peter, how did you "tap" the 100 watts?
Resistive divider? Kerry VK2TIL. 12838
| 2016-05-17 12:39:00
| peter_dl8ov
| Re: UHF Power Meter Detector Diodes
| Correct, see the W7ZOI RF power meter for details.
Peter DL8OV | |||||||||||||||||||||||||||||||||||||||||||||||||||||||
