ARRL

Secure Site Login

Forum Home - Rules - Help - Login - Forgot Password
Members can access, post and reply to the forums below. Before you do, please first read the RULES.

FT-991a Audio buzzing 2m and 70cm

Jan 5th, 11:47

ckperry

Joined: Mar 23rd 2018, 18:18
Total Topics: 0
Total Posts: 0
Hello,

I have an odd issue with a new to me ft-991a. I have factory reset the radio and programmed in some 2m/70cm repeaters via RT systems software and repeaterbook.com (also tried manual programming). I have the following issue:

I can receive audio from various repeaters in my area just fine, really great in fact with many having full quieting.

When I try to transmit on any repeater that just uses csq that is fine.

When I try to transmit on any repeater that uses a tone all that comes through the repeater is loud buzzing. This is true for 2m analog, 2m digital, 70cm analog. 70cm digital worked as expected!

HF operations appear just fine.

I have tried various power levels, cables, antennas and locations.

It appears to be something about the radio itself. I don't understand how 70cm digital can work fine but the other vhf/uhf/SF modes all have buzzing.

Again, I have reset the radio and programmed via software and manually. I do unlock the repeaters with tones but nothing but buzzing is coming through. 2m digital has buzzing but 70cm digital was crystal clear.

Any ideas on what is happening?

I have an email in to Yaesu support but who knows if or when I might hear back.

Thank you for your time and help.

Chris
KY4CKP
Jan 6th, 11:05

W1VT

Super Moderator

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
How are you monitoring your signal? Perhaps the buzzing is a feedback issue if you are hearing the signal while you are transmitting. There may be enough delay with the 70 cm digital to get rid of the feedback.

Zak W1VT
ARRL Senior Lab Engineer
Jan 6th, 11:47

ckperry

Joined: Mar 23rd 2018, 18:18
Total Topics: 0
Total Posts: 0
I've received reports from several other operators from the various repeaters I have been testing through. The closest repeater is about 8 miles away, the furthest is about 70 miles. I've used different cables, locations, power supplies and antennas. Without knowing the internal design of the ft-991a it still seems odd that:

1. 2m digital has buzzing
2. 70cm digital seems fine
3. 2m analog with tone through a repeater the repeater unlocks but the audio is all buzzing.
4. 2m analog without tone through a repeater seems fine.
5. 2m simplex seems fine.

Reception is all fine (including HF). HF transmission seems fine.

PS: Some of my testing was done in the field portable, so it does not appear to be my shack.

Chris
KY4CKP
Jan 6th, 17:12

W1VT

Super Moderator

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
Perhaps the tone generator is too loud or has harnonics that are audible.

Zak Lau W1VT
ARRL Senior Lab Engineer
Jan 9th, 10:52

ckperry

Joined: Mar 23rd 2018, 18:18
Total Topics: 0
Total Posts: 0
That has been suggested by my local Elmer, do you happen to know if there might be a pot or something that is user adjustable? Also, any idea why 2m digital is buzzing but 70cm digital was fine? That has me confused as well, my limited understanding for the digital is it does not use a tone in the same way that 2m/70cm analog do.

Thanks for the information.

Chris
KY4CKP
Jan 9th, 13:34

W1VT

Super Moderator

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
I didn't see anything in the instruction manual. That isn't normally a user adjustable function, as you normally need a deviation meter or spectrum analyzer to set that.

There is a 1750Hz tone activated by a button on the radio. Perhaps that could be the buzzing?

Zak W1VT
ARRL Senior Lab Engineer

Back to Top