Do I need a NanoVNA before operating radio?

[BIC2]

My first post. New to amateur radio. My wife and I just passed the Technician test; she also took and passed the General. I skipped that one for now. We purchased some new VHF/UHF equipment from a local brick & mortar, to include a Yaesu FTM-500D, a SamlexPower SEC-1235P-M and a Diamond X300A antenna.

I've installed the 10 ft antenna in my attic. I already had 75 ohm RG6 coax running from the attic to a distribution box in the basement. Not the 50 ohm preferred but we'll have to make do. I also have some solar panels that will interfere with reception to the southeast.

When we took the test, I was asking a proctor about the coax. He didn't know. My question is: should I use RG6 from the room wall plate to the transceiver, maybe 5-10 ft.? I ask because I have a box-full of RG58 and/or 59 and would use something I have instead of trekking out for some RG6. I estimate the length of a coax run from attic to basement to wired rooms to be 50 to 75 or maybe 100 ft.

As far as connectors, there will be one splicer in the distribution box and one at the end-room wall plate. I am also going to add a 90* right-angle connector to the wall plate. Is this setup OK?

More importantly, one of the proctors said I needed a NanoVNA to measure the SWR is below 1.7-1.8:1, before turning on my transceiver to avoid possible damage. Then he softened that a bit when I said I bought the recommended equipment at the shop. He said it was probably OK since the shop would have told me if I needed the NanoVNA.

Can I / should I get the NanoVNA before turning on the equipment or can I get that later if useful for other stuff? Thanks.

 

[AB5ID]

Listening to the radio is perfectly fine, regardless of your SWR. Owning a VNA is a luxury we could only dream of back in the day. If you're unsure about your SWR, use very low transmit power with an internal or external SWR meter to check your match. Eventually, I recommend running a straight, "clean" line of 50-ohm coax with as few of adapters as possible.

 

[k6cpo]

You might find someone with a conventional antenna analyzer that might let you borrow it to check your installation.

 

[mmckenna]

75Ω coax isn't ideal, but it'll work.

Couple of things I'm concerned about:
The number of connectors/"splicers". That's a lot of points of failure, additional loss, possible issues. I'd recommend setting everything up and testing by tuning in to a know good station some distance away from your home. NOAA weather broadcast might be a good idea.

An SWR meter would tell you most of what you want to know. Cheaper than a NanoVNA, easier to use, easier to understand.

An antenna in your attic can work fine, but you want to make sure there is no metal between the antenna and the outside. That means no metal roofing materials. No foil backed insulation/vapor barrier.
The metal in the solar panels might be a challenge, depending on how close they are. Also, how much RF gets into the solar power system would be something to be aware of. A smaller antenna outside (if your HOA/wife approves) might be a better approach.

SWR is something to be concerned about. I'd want it below 2:1. 2.5:1 or higher is getting sketchy. The RG-6, being 75Ω is going to throw the SWR off, but probably not drastically.

Long term, the NanoVNA can be useful, but knowing how to properly use it is a bigger concern. There's a lot of videos on YouTube regarding that. A few of them are even accurate/good, but there's a lot of bad videos. Make sure you find one that explains it in a way you understand. You also want to consider upgrading to better coax down the road. That will improve performance. Keep cable as short as possible. Using something that is 50Ω, correct connectors, no adapters.

As you've discovered with the test proctors, not all advice is good. But it's a hobby and it is time to learn, so you'll find your way.

 

[WA8ZTZ]

First, don't worry too much about the RG6 for now... the slight mismatch will not likely be a problem.
However, it would be nice to be able to check the installation with a SWR meter (especially given all the connectors involved).
Go to the local hardware store and pick up a 10' RG6 jumper cable for the run from the wallplate to the radio.
You will also need a "F" to SO239 adapter at the radio as well as at the antenna.

 

[BIC2]

In the attic, in addition to the solar panels, I do have a lead stained glass window on the opposite side. There is some foil backed foam board insulation and the composite roof does have metal valleys (as does most any roof).

If the attic doesn't work, I have an idea for a discreet outdoor antenna against an outside wall with a new 50 ohm coax run with an option of no connectors in the basement. I can also do no connectors in the basement now although I prefer the radio in a room upstairs.

I'm ready to purchase a SWR meter. Can I get some recommendations? At DX Engineering, most seem to run $100-200. On Amazon $20-60. I'd like the next day free delivery of Amazon but not essential. Thanks.

 

[K4EET]

<snip>

As far as connectors, there will be one splicer in the distribution box and one at the end-room wall plate. I am also going to add a 90* right-angle connector to the wall plate. Is this setup OK?

<snip>

Firstly, welcome to Radio Reference and congratulations on both you and your XYL getting ham radio licenses! Amateur Radio is a great hobby.

Secondly, just to clarify, since 75 ohm coax is usually run for CATV applications, when you talk about the “splicer” at the distribution box and the wall plate, are the splicers “barrel connectors” with F connectors on both sides of the barrel connector or are the splicers “3-way splitters” with two F connectors on one side and one F connector on the other side?

Just asking because 3-way splitters would introduce about 3 dB of loss each on receiving and if transmitted through, the splitters would definitely not survive and may potentially explode depending on the RF power level used.

Finally, I hope the splicers are just barrel connectors which should be able to handle the 50 watts of VHF/UHF RF power from your Yaesu FTM-500D transceiver. By the way, that is a very nice rig. I have one too. Nice to meet you and don’t hesitate to ask questions whenever needed.

73, Dave K4EET

 

[BIC2]

Secondly, just to clarify, since 75 ohm coax is usually run for CATV applications, when you talk about the “splicer” at the distribution box and the wall plate, are the splicers “barrel connectors” with F connectors on both sides of the barrel connector or are the splicers “3-way splitters” with two F connectors on one side and one F connector on the other side?

While the distribution box does have a 3-way splitter I was not planning on using it. I was intending to use an F barrel connector. Earlier this year, I "cut the TV cord" so no longer need it. Thanks for the warning, I was not aware of the danger.

Since I'm already looking at a lot of connectors, does using two F to N adaptors add to the concern? Thanks.

 

[mmckenna]

Since I'm already looking at a lot of connectors, does using two F to N adaptors add to the concern? Thanks.

All adapters add some amount of signal loss.

The amount of metal around your antenna may be an issue.

Mounting outside may be better, but you don't want the antenna flat up against the wall. The wall is going to have foil backed vapor barrier, likely, and that is going to be an issue. There is a good reason why antennas are mounted up high on top of homes/buildings. If you want them to work well, you need them up as high as you can get them and in the clear.

A straight run of 50Ω coax with no adapters would be a better solution. Do keep in mind that you want proper lightning protection installed where the coax enters the home from outside. That can be a big job depending on where your antenna is installed.

An SWR meter doesn't need to be expensive to work well. Not a fan of the really cheap Chinese stuff, but I ran a cheap MFJ meter for many years when I was first in the hobby. I think it was around $30 at the time. If you have the budget, go better. If you plan on getting a NanoVNA down the road, blowing a lot of money on a high end SWR meter may not be worthwhile.

Sounds to me like you bought a lot of equipment really quick without having a really good plan on how to make it all work. That's not uncommon for newcomers to the hobby. I'd recommend taking a step back and rethinking everything carefully. It'll make for a better system in the long term.

 

[BIC2]

I've added a Daiwa 501H meter to my existing Yaesu FTM-500D, SamlexPower SEC-1235P-M and Diamond X300A antenna. In my attic, I was getting no signal to the 75 ohm coax running to the basement. I then moved the equipment to various rooms in the house and outdoors, hooking antenna directly to radio, bypassing house-wide coax.

Testing results varied. I could get some of the 5 NOAA weather stations ranging from poor to excellent. From the living room, the meter showed power out of 50 watts, reflection of 0.1 and SWR of 1.1-1.2 . At another time, got 53 w and 0.0 reflection.

From under a suspended garage in the walk-out basement, I got 50 w and 0.0 reflection but only received one NOAA station.

Moving outdoors at ground level, had 40-50 w, reflection of 0.5 - 0.9 and SWR of 1.9 . NOAA was about the same as indoor, 5 stations of varying quality.

Outdoors but on a deck about 12 ft higher than ground, 50-58 w, 0.1-0.2 reflection and SWR 1.5-1.7 .

On a hunch, I purchased a coax tester and discovered the builder's sub had mislabeled the antenna coax. I gave the attic another whirl (not an easy task) with the 75 ohm TV cable to the basement distribution box. NOAA reception was comparable to all the other test locations. But, only 30 watts out, 0.5-0.6 reflection and SWR of 2.5 .

Next step is a real-world test; see if we can talk to somebody. The most convenient & current location for the antenna would be the attic. Any thoughts on the various setup locations? Thanks.

 

[BIC2]

My preference would be to keep the antenna in the attic but the SWR is 2.5 . Would an antenna tuner be a solution? Thanks.

 

[K4EET]

My preference would be to keep the antenna in the attic but the SWR is 2.5 . Would an antenna tuner be a solution? Thanks.

It appears that the Diamond X300A VHF/UHF antenna itself is not tunable to lower the SWR. Bummer. Is the antenna mounted away from any metal? Have you tried moving the antenna to different locations in the attic to see if the SWR would come down any?

 

[BIC2]

Update. Purchased a used MFJ 922 tuner. It's a discontinued model that will tune VHF & UHF. On VHF, tunes to a perfect 50 watts and 1.0 or 1.1 SWR.

UHF, not quite as good. I can have ideal power or SWR, but not both. Since my Samlex power indicates 9-10 amps when transmitting at 50 watts, I was informed I shouldn't worry about the 2.5 or so SWR because the Yaesu FTM-500D has a safety feature that protects the radio.

 

[mmckenna]

Update. Purchased a used MFJ 922 tuner. It's a discontinued model that will tune VHF & UHF. On VHF, tunes to a perfect 50 watts and 1.0 or 1.1 SWR.

UHF, not quite as good. I can have ideal power or SWR, but not both. Since my Samlex power indicates 9-10 amps when transmitting at 50 watts, I was informed I shouldn't worry about the 2.5 or so SWR because the Yaesu FTM-500D has a safety feature that protects the radio.

Well, keep in mind that a tuner only hides high SWR. It doesn't fix it.

"Ideal power or SWR" sounds about right. The radio will ramp down power usually with high SWR, as you were told.

What part of the UHF band are you trying to get the radio to work on?

 

[BIC2]

@mmckenna , what are the practical consequences of hiding vs fixing the SWR? Any performance, equipment safety, etc. issues?

UHF band? I'm new to this and just trying to get the equipment working at this point. Think I was randomly testing at 445.000.

 

[mmckenna]

@mmckenna , what are the practical consequences of hiding vs fixing the SWR? Any performance, equipment safety, etc. issues?

UHF band? I'm new to this and just trying to get the equipment working at this point. Think I was randomly testing at 445.000.

If the antenna is properly tuned for the band/frequencies you are using, it'll be more effective. High SWR means that some of the RF power is reflected back down the coaxial cable and doesn't get radiated.

No safety issues, and most radios will handle a reasonable amount of reflected power just fine. Most good radios will throttle back the power to prevent damage.

It's always better to have a properly tuned antenna if you can.

The antenna tuner just makes the antenna look good to the radio, it does't change the actual tuning of the antenna.



But, don't get hung up on SWR if it's "reasonable". Usually 2:1 SWR is fine. It's only a slight offset and it's not going to damage anything. If the antenna can be physically adjusted so it's resonate on the band you are using, that's better than adding an external tuner.

 

[devicelab]

Can I / should I get the NanoVNA before turning on the equipment or can I get that later if useful for other stuff? Thanks.

Yes absolutely. You'll learn a lot using it. If you like the hobby (which is sounds like you do) then it'll pay for itself in the long run. The cheapest units have a smaller screen and can be hard on the eyes. I'd recommend the NanoVNA-F V2 model (which is like $150-ish on Amazon.) This unit is more accurate and stable than the original NanoVNA -- larger battery and screen too.

There are more expensive models out there but start with that one.