Is my SW-102 and/or DB25-G working correctly?

[WRQV528]

When I first connected my Surecom SW-102 and a 100W dummy load to my DB25-G with a standalone power supply, I was pretty disappointed with what I saw. It peaks at about 13.9W (it is marketed as a 25W radio), and then falls from there. So I wanted to take more measurements, and compare them to other radios to see if something other than the DB25-G is at fault... and my reaction is "say it isn't so!"

This evening I spent about 2–3 hours taking measurements with all of my radios. For each channel, going in order from left-to-right as listed in the table of readings below, I would transmit for about 60–75 seconds, and the number I would record is part the power reading I saw the most of that time (the mode), part the average (so the number is slightly subjective). There would be only a brief break in between each trial; except for the DB25-G where I would wait for the fan to spin down completely, which I would guess takes less than 10 seconds. VSWR with the dummy load varied between 1.00–1.03, and VSWR of the antenna got as high as 1.77; though I was not paying too much attention to it throughout all the trials. Let me know if I need to provide more information on my testing "methodology" and/or my equipment.

 

Is there anything weird about these readings (other than that the UV-5R Plus was surprisingly consistent compared to all the others)? Why am I not getting a reading from the 0.5W channels on my KG-935G? And, most importantly, is my DB25-G underperforming?

 

[SteveShannon]

2 minutes ago, WRQV528 said:

When I first connected my Surecom SW-102 and a 100W dummy load to my DB25-G with a standalone power supply, I was pretty disappointed with what I saw. It peaks at about 13.9W, and then falls from there. So I wanted to take more measurements, and compare them to other radios to see if something other than the DB25-G is at fault... and my reaction is "say it isn't so!"

This evening I spent about 2–3 hours taking measurements with all of my radios. For each channel, going in order from left-to-right as listed in the table of readings below, I would transmit for about 60–75 seconds, and the number I would record is part the power reading I saw the most of that time (the mode), part the average (so the number is slightly subjective). There would be only a brief break in between each trial; except for the DB25-G where I would wait for the fan to spin down completely, which I would guess takes less than 10 seconds. VSWR with the dummy load varied between 1.00–1.03, and VSWR of the antenna got as high as 1.77; though I was not paying too much attention to it throughout all the trials. Let me know if I need to provide more information on my testing "methodology" and/or my equipment.

 

Is there anything weird about these readings (other than that the UV-5R Plus was surprisingly consistent compared to all the others)? Why am I not getting a reading from the 0.5W channels on my KG-935G? And, most importantly, is my DB25-G underperforming?

 

The SW-102 might not be reading correctly. There are a few examples of that on this forum. 

[marcspaz]

The Surecom SW-102 is designed to be calibrated by the end user.  While there is a chance it's accurate out of the box, it's not always.  There is a possibility that you need to have your meter calibrated. 

 

[Newb]

In the beginning...Oh wait! My first purchase for an SWR/Watt meter was a Workman Model 104 analog meter along with a DB20-G, a Tram/Browning BR-450 5/8 over 5/8 and mag mount.  No matter what I tried I could not get my SWR below 2!  My next purchase was a 100 Watt dummy load.  My back ground is from the GOLDEN age of CB.  No digital stuff!!!  With the dummy load instead of the antenna I still had almost 2 for an SWR.  A dummy load should be very close or at 1.00:1. 

Out comes the phillips screw driver and the enclosure for the meter is open.  Analog meters for SWR are tuned with a LOOONNNGGG legged capacitor on the input and the output SO239 connectors.  Moving the capacitors will effectively tune the meter.  The input side usually doesn't make much difference so I concentrated on the output side. The cap legs were bent in a U shape so I slowly straightened the U a little at a time (noting the original position and shape, cell phone camera!).  Key up and check the meter.  If the meter is getting closer to 1:1 you are headed the right direction.  Not sure why this meter was so far out of calibration, but a few tweaks later and the needle on the meter just barely moved.  Don't attempt to move the cap with the rig keyed up as touching the cap with ANYTHING changes the capacitance and will skew the reading.

All that ancient history in hand, I would be interested to know how to calibrate one of these digital gizmos as I don't see any instructions for my Latnex PM-100W for calibration.  Beuller, Beuller.

[Newb]

OOPPPSSS by the way, when I adjusted the SWR to be correct the wattage of the meter also came into line from 13 watts to 18+/- watts.

[WRQV528]

On 7/8/2022 at 1:29 AM, marcspaz said:

The Surecom SW-102 is designed to be calibrated by the end user.  While there is a chance it's accurate out of the box, it's not always.  There is a possibility that you need to have your meter calibrated.

Is there any documentation or how-to(s) on calibrating this model? I have not been able to find any.

[marcspaz]

12 minutes ago, WRQV528 said:

Is there any documentation or how-to(s) on calibrating this model? I have not been able to find any.

 

Not that I am aware of.  The adjustments are all in the menu. 

 

Honestly, and believe me I am not writing this to be mean, but if you don't know how to do it based on training and experience, you probably should try to find any either.  Just my opinion... without the correct training and alignment tools, its likely not going to be possible to align it yourself.

 

Do you have an friend that have a high-end meter that is known calibrated, so you can run a comparison as you make the adjustments?  That friend would likely be able to assist. 

[Newb]

 

[Mikeam]

I guess I got lucky as my surcomm was right on with 2 Kenwood radios and the KG1000. Friend is a ham and we also tested the same radios with his equipment and had the same results.

[wayoverthere]

1 hour ago, Mikeam said:

I guess I got lucky as my surcomm was right on with 2 Kenwood radios and the KG1000. Friend is a ham and we also ested the same radios with his equipment and had the same results.

Same here...pretty spot on between the sw102, sw33, and nanovna.

[WROZ250]

Surecom concerns aside, the DB-25G (nor any of it's relabeled cousins) does not put out 25W, regardless of the advertising.  I have three variants of this radio, all 100% identical save for the label and they all pretty much put out ~18W max at 13.8 Vdc.  That said, it's a pretty decent radio for the price (~$100 USD).