Watt Meter repair and modification advice needed

[KL7OF]

I have 2 wattmeters that were obtained a hamfests....A SWAN WM 1500 and a MATTCO PX 1000...Both do not work.  The meter movements seem OK and no visibly scorched components inside..I found a schematic for the Swan and was unable to find anything on the Mattco...Looking for advice on how to test these circuits for repair..
I am also wondering if there is a simple way to boost the power handling capability of either of these units....I would like to have a wattmeter that would read at 3KW or4 KW...Any ideas?...Thanks Steve

[WA1GFZ]

Sounds like blown diodes. Use 1N5711 or 1N4148.
If the pickup is a line going through a toroid then just add turns of wire on the core. Multiply the turns by 1.4 to double the power. I would go to a bigger core if it is smaller than .68 inches for 4KW. It is a current transformer so more turns means less current to the secendary or  less output power to the rectifier.
I built a copy of the Collins watt meter that goes to 1KW. I just increased the series resistance to the meter to shift it to 2KW.
Lightning has taken out my reflected power diode when I forgot to remove the antenna during a storm.

[KL7OF]

In the Swan WM 1500the toroid is about .375 diameter so it looks like it will be too small for 4 KW....I have some toroids that are almost .750 that I bought for beverage antenna transformers....I could try one of those......Does the density of the toroid make any difference in this case?

[k4kyv]

Toss those worthless pieces of crap and order a Bird APM-16, or if in the likely event you won't want to spend that much money, search the net for a good thermocouple rf ammeter.

[W7SOE]

Toss those worthless pieces of crap and order a Bird APM-16, or if in the likely event you won't want to spend that much money, search the net for a good thermocouple rf ammeter.

Maybe someone can clue me into what is so great about Bird watmeters. I have a Swan meter and it seems to do the job. It is probably accurate to within 20 watts, who needs more?

I can understand that the Bird meters are rugged and accurate but they seem on the wacky side of expensive. And then you need to buy the plug-in element?  For over $100?  What is that, a shunt?  Solid gold?

Rich

[W3SLK]

Rich said:

Maybe someone can clue me into what is so great about Bird watmeters. I have a Swan meter and it seems to do the job. It is probably accurate to within 20 watts, who needs more?

Then you will be able to announce over the air your power out in "Bird Watts!!!" 

[KA2DZT]

I only use Bird meters for measuring RF power.  They are expensive.  They were a lot cheaper 25 years ago.  The thing about them is that 25 years later my Bird meters still work perfect.

Steve, you should be able to buy a used Bird 43 off ebay for about 150.  The elements have jump in price over the past few years.  I paid 40-50 for mine back 25 years.  The HF elements were always more than the VHF elements.

Most likely the diodes are toast in the ones you have, like WA1GFZ mentioned.

Don mentioned using a RF thermocouple amp meter which another way to measure power, if you know exactly what your load resistance is.

If you're looking for a peak reading meter, well that's another issue if you're using any of the above mentioned methods.

Fred

[KX5JT]

Rich said:

Maybe someone can clue me into what is so great about Bird watmeters. I have a Swan meter and it seems to do the job. It is probably accurate to within 20 watts, who needs more?

Then you will be able to announce over the air your power out in "Bird Watts!!!" 

OR you could just say "A little Bird told me I'm running a 374.9 Watts of Carrier"  -- they'd probably think you mean a Bird Wattmeter...

[KL7OF]

I have RF amp meters on several of my transmitters and I find the scale of such size that there is not much meter swing...harder seeing small changes...They also seem slower to react than most wattmeters...I have never had bird watts before..the meter seems smallish....I like a big meter with a lot of swing...Bird does however, seem to be the most available high power unit around...I saw a military 5 KW unit that was the size of a shoebox but it had a big meter..

[WA1GFZ]

3/8 is way too small for 4 KW, it will saturate. I used -2 iron (red) .68 inch. I have a mil coupler with 1 inch yellow (-6)
The best detector I've seen is to copy the Collins watt meter. There is a good article in the old red ARRL SSB handbook. I built mine in a small minibox with a pair of type N connectors on each side. A short section of RG393 with the shield terminated on only 1 side. I calibrated it with the bird. I think you can duplicate the performance if careful with layout.

[n2bc]

You might want to look into this:  http://www.telepostinc.com/lp100.html

[The Slab Bacon]

If you dig around at hamfests, the best bang for the buck is still the old military AN/URM 120. These can still be found in the $100 range with all 4 "slugs". Good from HF all the way to UHF. They are easily calibrated and quite accurate. Each slug has 4 power level positions and is easily calibrated for an exact operating frequency if needed. I have a Bird 43, but am too cheap to buy all of the slugs I normally need, so I still find myself using the 120 most of the time. I bought a pair of them some years back for $40 with all of the slugs to boot. (sometimes we get lucky) and still use them constantly to this day.

[KB2WIG]

  "  Maybe someone can clue me into what is so great about Bird watmeters. "

The Bird is the word.


klc

[Opcom]

Toss those worthless pieces of crap and order a Bird APM-16, or if in the likely event you won't want to spend that much money, search the net for a good thermocouple rf ammeter.

Yes they are inaccurate, and have been known to have radioactive meters and leak PCBs.
Please mail all apparently working and unwanted wattmeters to me postpaid for proper disposal. I am good on QRZ.

[KM1H]

Any POS can become accurate if you calibrate against a Bird . Create a cheat sheet for the frequencies and power you want.

BTW, I need a 100W 2-30 Bird 43 slug, mine took a walk

Carl

[KL7OF]

Carl, I saw a site that tells how to take apart a bird slug and repair it..I'll post the link if I run across it again...  Steve

[Fred k2dx]

Watch for Sola/Dielectric meters at hamfests. The elements interchange directly with Bird and Coaxial Dynamics. The 3 1/2" meter is larger than the Bird 43's and makes it much easier to view small changes.  The shape makes it much more stable for use in the shack, especially with RG8U type cables. The Bird 43 series is better suited for field use. I have one of each... my Sola Model 1000 has served me well for a long time. It was purchased from a trusted seller at a hamfest years ago and was old then. The newer 1000a model has a different style meter but should be as good.





Here's a link to one source: http://www.nm3e.com/prod01clones.htm

[KB2WIG]

F,

Thbbft!  Sola/Dielectric watts are not as good as Bird watts. What whatts do you think Bill is pining for?


klc

[W7SOE]

If you have one watt meter you know your power level; if you have two you know nothing.

Rich

[WD8BIL]

FGI:The Sola/Dielectric meterline was purchased by Coaxial Dynamics > 20 years ago.

[KL7OF]

Google..."A photo tour of a bird wattmeter element"

[WD8BIL]

One word of caution to anyone who intends to repair their elements.

The positioning of the pickup loop and any other "tabs" in the sampling area of the elements must be handled with care. Their positioning is critical to the directivity and frequency response of the element.
These are pointed out in the attached photos.

photos by WA1MIK and VE3YX

[KM1H]

Carl, I saw a site that tells how to take apart a bird slug and repair it..I'll post the link if I run across it again...  Steve

By walked I mean literally, I cant find it!

Id appreciate that link if you find it. I also want to try to adapt a 50 to 75 Ohms.

Carl

[WD8BIL]

http://www.repeater-builder.com/projects/bird-element-tour/bird-element-tour.html

In the article, Carl, he explains getting the teflon cover off. There's 2 ways it is held on.
Some have screws holding it from the topside under the cap.

The snap on ones come off easier ifn you freeze the teflon first. I put crushed ice in a shallow bowl and place the element's teflon cover in the ice for 5 minutes.

[k4kyv]

If you have one watt meter you know your power level; if you have two you know nothing.

Rich

Touché!