Tag Archives: QRM

Why a strong activator might not hear your call

I had a conversation recently with a ham who upgraded his license for HF privileges primarily to do park activations in the POTA and WWFF programs.

He mentioned that he had a few successful park activations under his belt but was left scratching his head on a couple of occasions when he attempted a Park-To-Park (P2P) contact but could not be heard by the other activator.

He did all of the right things: announced his call sign followed by “Park To Park” twice and was patient while the activator worked a small pile-up.

In one case, he said the other operator had an incredibly strong signal–and having always heard, “if you can hear them, you can work them“–he was really baffled that he couldn’t make contact especially being a desirable P2P. His activations were successful so he knew it wasn’t an equipment issue.

He asked for my input, so I thought I might share a few points here as this is not at all uncommon–please comment if you think of others:

Big power, small antenna

Some activators operate mobile and don’t actually deploy their gear in the field. They simply drive up to a site, turn on their mobile HF rig in the car, and start making contacts with the mobile whip antenna mounted on their vehicle. There’s nothing wrong with this approach in the POTA program (just keep in mind mobile activations are not allowed in SOTA). Mobile activators can rack up numerous park activations in one day often regardless of weather or any site restrictions.

Mobile vertical antennas like Screwdrivers, Hamsticks and whips are quite impressive and, many activators swear by them. Not only do they work well in mobile situations, but they can also be quickly set up on a tripod in the field and many models can take a full 100+ watts of power.

If an activator is pumping 50-100 watts into a small, resonant mobile antenna, their signal is getting out there. But since their antenna might not actually have a lot of gain or efficiency on 40 or 60 meters, it can’t compete–in terms of reception–with a large aperture wire antenna.

In this scenario, the activator might be logging a load of stations, but they may not be able to hear your signal if it’s weaker than the others in the pile-up.

QRM on the other end

Often summits are the location of clusters of commercial transmission antennas and towers that can cause interference

This is a big one, actually, and affects both park and, especially, summit activations.

Sometimes the other activator’s site is plagued with QRM (radio interference) emanating from power lines, nearby buildings, transmission equipment, and other electronic sources.

That QRM will not typically affect their transmitted signal, but it will have a dramatic impact on what they can receive and hear.

For example, I recently attempted to activate a game land I’d never been to before.  On Google Maps satellite view, the site looked pretty darn remote and there were no buildings in sight. When I arrived on site, I set up my station, spotted myself, and started calling CQ POTA.

When I turned up the volume on the radio, it hit me that my noise level was a solid S8-S9! Turns out, there was a nearby power line that was spewing broadband noise across the entire HF spectrum. It was pretty much inescapable–there were no unaffected HF bands.

Had I really wanted to continue with that activation (I did not) I would have only been able to work stations with signals that were above my high noise floor. Perhaps one in five contacts at best. My chasers would have all been been left scratching their heads.

QRM isn’t always S8, but even an S5 or S6 noise level might wipe out 40-50% of the signals the activator can hear.

While hitting the field is usually the best way to escape QRM, there are spots that are as noisy an an urban neighborhood.

QSB

This is a big one; especially with the unsettled conditions we’ve had over the past couple of years.  QSB, or signal fading, can be a proper obstacle in completing a contact.

If you’ve been watching my activation videos, you’ve no doubt seen chasers that call me with a 599 signal and when I respond to them, I hear nothing but silence. In those situations, I’ll repeat my reply with their callsign and signal report a few times in a row. I do this because QSB is a bit like having a three year old playing with your volume control while you’re on the air.

Seriously, imagine that three year old turning up the volume, then turning it back down, then turning it up again, and so on. It essentially has the same effect. Sometimes QSB is shallow and slow, other times it’s deep and fast–or it can be any variation in between (including deep and slow which is the worst).

In those situations as an activator, I reply a few times in a row with hopes to catch the QSB on the upswing  so I can have a window of contact with the other station. When I do make contact, I try to keep the contact as short as possible so there’s hope for a complete exchange.

As a hunter, you have less control because your only hope is that QSB will be at the peak of signal strength when you call the activator.

Environmental distractions

If you’ve been doing park and summit activations for very long, you’ve no doubt experienced some “environmental distractions” during an activation.

I’ve been at parks before when the grounds crew were blowing leaves, mowing, and using other lawn equipment. It can be proper audio QRM especially if you don’t have an option to wear headphones to isolate those noises.

Sometimes the wind can cause a lot of extra noise. I’ve also been in shelters where the rain hitting the tin roof (while somewhat soothing) adds a lot of extra noise.

I’ve also been on summits and in parks where other hikers and passersby start asking questions while I’m in the middle of handling CW contacts.

My buddy Vlado (N3CZ) draws a crowd during a joint park activation on the Blue Ridge Parkway

They don’t understand that you’re actually in the middle of an exchange and need your attention focused. 🙂 For so many of them, it’s the first time they’ve ever seen/heard someone operating Morse Code and they’ve loads of questions. I hate to pass up an opportunity to promote amateur radio, so I’ll often pause the activation to talk with them.

In summary

If you know your radio equipment is functioning as it should but you can’t seem to grab the attention of an activator, keep in mind that it’s likely them, not you.

They’re not ignoring you, they simply can’t hear you.

The best practice for eventually making contact is to be patient and persistent. If you’re an activator trying to work another activator for a P2P or S2S (Summit To Summit) contact, keep sending P2P or S2S with your call. Often, other hunters will hear you and point out to the activator during their own exchange that there’s a weak P2P or S2S operator calling. More often than not, that’s your ticket to busting through!

Did I miss something? Please comment and share your thoughts and tips!