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Surecom SW-102VU


tdukes
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Just an FYI, your mileage may vary!

I bought this meter due having issues with a Latnex meter not correctly calculating SWR. Seems the Surecom is no different.

Apparently, the newer models have this issue. Older models do not. Contacted Surecom about this and they are playing dumb when I presented evidence to back this up.

I'm not a radio expert by any means but I feel I'm pretty confident I can read a cutting chart by a antenna manufacturer and can measure twice and cut once. I don't think I can get the SWR to 1:1 on two antennas. If so, I need to buy some lottery tickets.

I think its an issue with the advertised frequency range. I checked it on a ham frequency of 146.52 and got a 1.72 SWR. Some of that could be the antenna isn't tuned for that frequency but it shows it can report something other than 1.0.

This antenna was checked with a NanoVNA that was calibrated just prior to the test. Notice the difference in SWR.

 

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Do you have transmitters with higher output power... like 50W, to test that meter.

The sensitivity for the reflected power side may be similar the forward power side, and just incapable of reading the minuscule power being reflected by a 5W HT. MFJ-847 ( https://mfjenterprises.com/products/mfj-847 or https://www.hamradio.com/detail.cfm?pid=H0-014171 ) at least seem to handle HT power levels (though on the BTech GMRS-V2 [early version, highly under the 5W/0.5W spec] it can't measure reflected on the low power setting -- same for Wouxun KG935 -- though it also doesn't seem to like that unit... at high power its shows nearly 100% reflected! Looks like it's time to order a new antenna [the Nagoya 771G from the BTech on this shows reasonable values])

 

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BTech low power

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BTech high power

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Wouxun low power stock antenna

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Wouxun high power stock antenna (it looks like it's reading MORE reflected power than forward power -- but that may just be camera catching the LCD refresh cycle)

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Wouxun high power NA-771G antenna

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I've mentioned this before... but u may not have explained it correctly.

 

There is likely nothing wrong with the Surecom. It is a device designed to be calibrated by the end user. While many come from the factory pretty close, you likely need to calibrated yours. Just calibrated it against the Nano VNA, if that's what you have, and check it again. Even if it's not dead perfect, it will be close enough. 

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9 minutes ago, marcspaz said:

I've mentioned this before... but u may not have explained it correctly.

 

There is likely nothing wrong with the Surecom. It is a device designed to be calibrated by the end user. While many come from the factory pretty close, you likely need to calibrated yours. Just calibrated it against the Nano VNA, if that's what you have, and check it again. Even if it's not dead perfect, it will be close enough. 

How nice... A meter that requires one to already have a meter in order to set the correction factors (apparently high and low power adjustments in %, if I interpreted the fine print in the manual). Not sure how one would adjust it based upon a NanoVNA as that is flea power for testing antenna/transmission lines, and probably won't even show up on the Surecom if one puts it between the VNA and an antenna)

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I'm not sure what your experience is, but in my experience, all meters must be calibrated. I'm sure you calibrated the Nano VNA per the directions, correct? Otherwise I wouldn't put much value in those readings. 

 

Granted, there are some meters that are sold being advertised as calibrated or not user adjustable, but a quality version costs many hundreds of dollars and should still be professionally calibrated regularly. That is just how this stuff works. 

 

Don't use it with the Nano VNA at the same time. Take the reading with the VNA and document it.  Then take a reading with the Surecom, make a minor adjustment, and then retest. Just repeat that process until your readings match. If you have more than 1 antenna to test with, to ensure they are at least close to the same readings once it's calibrated, that would be a good verification. 

 

Edit: I see you're using an MFJ meter, not a Nano VNA... my mistake. 

Edited by marcspaz
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1 hour ago, marcspaz said:

Edit: I see you're using an MFJ meter, not a Nano VNA... my mistake. 

I have both, along with Diamond SX-200 (which covers HF-VHF), along with two MFJ antenna analyzers (with limited capabilities on UHF)..

My concern was that, with both high and low power tweaks (I'm presuming those apply to forward and reverse, respectively) in the Surecom -- which is proper? The VNA may show actual SWR, but that SWR is the result of comparing forward and reflected power, and that makes for a spectrum of adjustments in the Surecom -- do you accept the forward (high) power reading and tweak the reflected (low) power up/down, do you tweak the forward to display /rated/ output power of the radio, and THEN tweak the reflected until the SWR matches the VNA, etc..

(The SX-200 is a single needle meter, in which one uses a "Cal" position to set whatever the actual forward power may be to "full scale", then flip the switch to "SWR" which is essentially based on the reflected power scaled by the "Cal" dial -- similarly, forward and reflected power are separate switch positions [it also has a peak/avg button]. While it doesn't reach UHF, I can at least compare it against the MFJ, and get similar readings from my 100W TS-2000 on 2m (both show ~85-88W - so two meters separated by decades and by different manufacturers would appear to have similar miscalibration, or my TS-2000 is under performing on 2m).

I bought the NanoVNA mainly because I'm tired of doing manual frequency sweeps with the MFJ antenna analyzers.

ADDENDUM: While there is a screw for the battery compartment, I suspect gaining access to sensor board would require mangling the back specification label (metal, not paper). Said label states 0-120W +/- 5%

 

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So, just for grins and giggles, I took some readings on one of my antennas...

 

MFJ Analyzer

145.520 = 1.0:1

147.000 = 1.3:1

 

Nano VNA

145.520 = 1.2:1

147.000 = 1.2:1

 

Surecom

High Power

145.520 = 1.1:1 / 46.07wFwd / 0.131wRev

147.000 = 1.08:1 / 41.22wFwd / 0.061wRev

 

Low Power

145.520 = 1:1 / 5.1wFwd / 0wRev

147.000 = 1:1 / 4.67wFwd / 0wRev

 

If you look at the readings, they are all close enough.  The truth is, they may all be correct.  It takes different cables and connectors to test with these devices and those numbers will change based on the changing of hardware.  Shoot, realistically, just disconnecting and reconnecting the same gear twice could give you these kinds of variations.

 

If we look at the Surecom reading 145.520 = 1.1:1 / 46.07wFwd / 0.131wRev... the reverse power is 0.285% of the forward power.  So, if we switch over to 5w of output, I am not shocked the meter is reading a 1:1 SWR, because 0.285% of 5w is too low for the meter to read.  Its about 0.014w.  the scale on the device doesn't have enough place holders displayed to show the SWR... so it rounds to zero (or 1:1).

 

I still think that TDukes needs to either calibrate the Nano VNA, the Surecom, or both.  But for what we do as GMRS users, I think the device is working as intended and is "close enough" to know our stuff isn't going to break.  The need to fine tune that last drop of power (maybe 40 miliwatts at 5w scale "if" his VNA is correct) is pointless except as an exercise. 

 

 

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