| NW2M |
Rating:  |
2018-01-29 | |
| Owned over 10 years |
Time Owned: more than 12 months. |
I purchased my AN/URM-120A at the Hamvention and have owned it for over a decade. My unit was very late in the series as it came with the fiberglass case and updated slugs (round knobs). I agree with all of the other comments and rating before mine. I think they are all very fair for anyone reading a review. We are dealing with something made in the 60s and 70s- but there are parts everywhere. I managed to get replacement diodes (looks like a .22 short) and different n-connector types. With parts very scarce, it is safe to say we will be looking for basket-case units to keep good units working. Scalpers know this... Each slug comes with a protective end-cap.
Here are the three slugs that came with my unit:
1: 2 - 30 MHz, 50, 100, 500, 1000 Watt
2: 25 - 250 MHz. 10, 50, 100, 500 Watt
3: 200 - 1000 MHz, 10, 50, 100, 500 Watt
I connected my unit with a Bird 43 with 50W and 100W slugs for calibration using a FTdx-3000 as the RF source (1.8MHz-54MHz) from 5W to 100W. I have taken the slugs apart for cleaning lubrication, and calibration. Everything is built like a tank. Just be aware that the time constant of the meter is quite slow. It behaves more like a liquid-filled meter. Allow 5-6 seconds for the meter to come to rest when taking a measurement. So watching SSB voice peaks on this meter is impossible.
The fiberglass case has two additional circular cutouts for more slugs. I purchased a round 100W dummy load with N-connector that is a perfect fit. There is a 7" slot in the foam for the manual and documentation. All very neat and tidy.
Best of 73, Al - NW2M |
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| W1BR |
Rating: |
2016-01-23 | |
| Great, with limitations. |
Time Owned: more than 12 months. |
Rating really depends on the calibration! Each slug is easily calibrated, but their ability to hold alignment is the Achilles Heel for these instruments! The slugs are set by an adjustment that sets the insertion depth for each slug during calibration. Wear, age, dirt, etc. can affect the long term calibration. The depth setting is really critical and a very minute change (wiggling the slug, etc.) will show a change in the power reading!
These are nice instruments,providing one can accept a few inherent weaknesses. They are usually priced at bargain prices, so if you can find a clean unmolested model that has the case and all of the slugs that came with the original kit I'd say go for it. A Bird 43 and all of the Bird slugs that would be needed to equal this unit would be out of budget for most hams!
I bought mine at a flea market for around 50 bucks. The calibration on the HF slug was way, way off... someone had played with the calibration. I used a Bird 43 wattmeter and several Bird slugs to get the alignment as close as possible. The problem is that even the Bird 43 meters need to be a decade better for accuracy and precision to do justice for a proper calibration. I've owned several Bird 43 wattmeters, and they also are NOT standards by any means.
This wattmeters sell cheap because of known problems. Anyone buying one should be aware of the meter's history--regarding storage, calibration, etc. And a new owner would be wise to have access to a comparable instrument to do A/B comparisons to ensure accuracy.
Despite a few known issues, these are very rugged, military grade instruments. |
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| VE3ZXK |
Rating: |
2011-01-11 | |
| Great Meter ! |
Time Owned: more than 12 months. |
| Great unit, owned it for several years, didn't use it much, as I bought a top-end meter soon after. The meter is a well-kept secret. I have owned Telewave, Bird, Philco/Sierra, and Motorola inline wattmeters. I like the Telewave best for VHF/UHF, and the Philco is a much better price for a HF and up wattmeter, if you have a supply of slugs, as I did. I even had the 5kW HF slug. |
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| KV6O |
Rating: |
2011-01-11 | |
| A well built, versatile meter |
Time Owned: more than 12 months. |
| I purchased mine around 3 years ago for about $150 on ebay. 3 slugs cover 2-1000MHz (or Mc as the slugs are marked) in 4 different power levels. I also have a Bird 43, but the URM-120 is my main meter on the bench. I just fixed the connector that attaches to the slugs today as the coax was weak at the connector point and the electrical connection was intermittent. It's not an SMA connector on mine - it's a Kings connector similar in size to an SMA but mechanically like a BNC - cam lock style. It came apart easily - silver/Teflon construction - and now it works like a champ again. Great meter, and a great price. |
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| AI4WM |
Rating: |
2008-10-04 | |
| Handy accurate meter |
Time Owned: more than 12 months. |
I've had mine for over a year and have used these for over 20. Nicer than the Bird since you do not need to purchase and carry and interchange all kinds of slugs for all kind of powers and frequencies. Every bit as accurate, but if you need parts they may be impossible to get except for purchasing a complete meter.
There were several versions of this meter made by both Douglas Microwave and Struthers. I think Struthers may be the new of the meters. Mine are Douglas and I have used both brands and noticed no difference in operation other than some of the Struthers have calibration adjustment to set a reference before measuring SWR.
On very low powers Bird may have an advantage because of the low power slugs available.
These are usually available for about $100 to $150 USD so you get more bang for you buck unless you buy one that has bad diodes.
73,
Bill
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| KE4AMQ |
Rating: |
2007-06-28 | |
| the best |
Time Owned: 0 to 3 months. |
| this meter is a great bargin i paid 150 for it had to do a little cleaning on it but wow what a meter. the bird 43 cant hold a candle to the urm120a. where could you find a meter that covers 2-1000 megs and upto 5000 watts on hf. great meter. |
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| AB9GO |
Rating: |
2005-05-06 | |
| Wonderful meter, but never use oil on it!!!!!!!!!!!!!!!!! |
Time Owned: more than 12 months. |
I have two of these and both are a very good value as long as you do not have to replace any parts on them. Pars are not commonly available except from a scrap unit. The diode in the slugs is made of unobtainium and working on the slugs is NOT for the novice. I have one that was the older Philco/Serria model and a much newer Struthers. (1980's ?) The Struthers was purchased in like new condition for $35.00 at a local hamfest. The seller told me that the knobs were slipping, but it was otherwise OK. The ultimate problem was the slug was lubed with oil and the plastic cam in the slug swelled up. As most might do, he forced the knob now stripping the hole where the metal shaft was pressed into the cam. I had to remove the cam, sand the cam in the area where the shaft was press fit so it would no longer bind and then drill the cam and the shaft to accept a roll pin, then sand the roll pin to length. It was a small pain in the b*tt, but when I was done I had a very well working meter. Use lithium grease (Lubraplate or equiv.) to lube the slugs on the newer Struthers or you will have to go through what I did. The older Serria uses a metal cam, but I would still not use oil on it. Lubraplate is the way to go.
Randy AB9GO
p.s. I agree that the Bird is a great meter also, ( I own one model 43 ) but the cost of all the 12 slugs to cover what the URM-120A does with 3 will break your wallet big time.
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| W2CSH |
Rating: |
2005-05-06 | |
| Beware |
Time Owned: more than 12 months. |
| This could be a very nice meter. The HF slug on mine had a shorted diode when I got it. It is impossible to find replacement diodes and almost impossible to find a spare HF slug. The diode is a MIL type ceramic and brass unit and does not cross reference to any known diode. I found one available at a surplus center in Norfolk Va and they wanted $440.00 for the diode. Its cheaper to buy another URM-120. Just be sure the unit you buy is warranted to have a working HF slug. A bird 43 may cost more but you can get millions of parts for one. |
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| W9LBB |
Rating: |
2003-10-28 | |
| Better than The Bird? |
Time Owned: more than 12 months. |
I picked up a URM-120 a few of years back, mainly because it was interesting, and the price was right. It appears to have been used Navy surplus that became available when a P-3 Orion sub hunter squadron in the area was deactivated. I didn't really need the beast because I already had a Bird 43, but I'm glad that I DID jump when this critter showed up.
I find myself using this Struthers built meter MORE than I use the Bird nowadays.
Comparing readings between the two meters showed that they're within 2% of each other; well within spec when you consider that the Bird is only speced to plus or minus 5% of actual forward power.
On the plus side for the URM-120 is the fact that it covers a HUGE frequency and power range with a small number of slugs, as compared to the Bird (those expensive little Bird slugs will eat you out of house and home eventually).
On the minus side, the URM-120 doesn't use easily changed connectors like the Bird; you're pretty much married to type N and some adaptors. A TDR check shows some minor imprdance bumps with this approach, but unless you're dealing with very small powers on VHF the error intorduced in inconsequential.
The URM-120 is a heavier and a bit more bulky package than a basic Bird outfit, but when you consider a Bird with an assortment of slugs and QC connectors that is pretty much a wash.
Both meters are ruggedly built and will last a lifetime unless you use it for pounding nails. I have a military one in the steel transport case, tho I've seen a few in molded plastic cases which I assume are civilian units. Both are good, but I personally prefer the steel cased unit.
The biggest advantage of the URM-120 is that it's a whole lot CHEAPER than a Bird usually, and it works just as well for nearly all applications, amateur and professional.
If I had the choice of buying a Bird or a URM-120 for the same price, I'd be hard pressed to make a reccomendation. However, since the URM-120 is almost always a LOT cheaper than a Bird, the choice becomes clear.
If it's in good shape (i.e., doesn't need to have repair parts chased down; unlike the Bird that CAN get difficult), and it has the full set of slugs (Bird slugs definitely will NOT work here!) the URM-120- is an excellent choice for most everyone.
73's,
Tom, W9LBB
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| WA0RXC |
Rating: |
2003-03-05 | |
| This meter is well suited for Ham use |
Time Owned: 0 to 3 months. |
| After using a Struthers AN/URM-120A for several weeks and comparing to my Bird 4410A I prefer the Struthers for station use. The basic principle of operation is the same for both units. A fixed RF line section and variable distance pick up elements for different power ranges. The elements are rotated to read forward and reflected power. The AN/URM-120A uses a silver plated SMA coax connector between the element and meter which to me is superior to the contact arm used in the Bird system. One of the problems I have encountered with the Bird design is a poor connection between the arm and element. This occurs mainly with older slugs. Three elements in the Struthers cover 2-1000 MHZ, 0-1000 Watts vs multiple elements required for the Bird. The Struthers has a direct reading VSWR scale and with the aluminum diecast housing, does not move around the shack with RG-8 coax connected. The Bird does have the advantage in portable operation. Meter size and accuracy seem about the same. I do not have access to a calibrated RF source to make real accurate measurements. With the sloping front on the Struthers the meter is slightly easier to view. Having paid $225 for the meter and three elements, I consider this an excellent value for an accurate wide range wattmeter. |
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