Low Microphone Audio
The VX-7 and other Yaesu HTs in the VX series are noted for low microphone audio. It is generally a BAD idea to increase the deviation through the service menu–then if you talk too loud, you will tend to experience “talk-off” through the repeater/receiving radio, because your transmit bandwidth becomes excessive and gets into the squelch circuit (more on this subject in the future).
I had read that piercing the microphone diaphragm (on the front cover, NOT on the mic element itself!) would improve the microphone sensitivity. I did pierce the thin diaphragm, and did note increased microphone sensitivity. Wind noise is frequently a problem in internal mics, and it did raise this issue slightly. However, I now can talk about 12 cm from the microphone in most cases and be well heard–before it was more like 4 cm from the microphone! Of course, I left the TX deviation adjustment as from the factory.
You should keep in mind that you are now inviting dust and water into the microphone element. I plan to reopen my Yaesu VX-7 and put a small piece of Motorola speaker felt into the cavity, to prevent most impurities from entering. I would not recommend just leaving the hole open as I did.
Maldol MH-209SMA antenna
I was pleasantly surprised upon some informal empirical testing with the Maldol MH-209SMA vs. the SMA503. The SMA503 has about 18 cm of radiating length while the MH-209SMA appears to have only about 5 cm. And, as you can see in the photo, when used in conjunction with the Yaesu MH-57 speaker-mic, about 2cm of the 5cm is blocked!
Still, as compared to an SMA503 with no speaker-mic, the loss seems to be no worse than 5 dB or so (both receive and transmit). This is true on both 2 meters and 440. I didn’t test it on 6 m or 220 MHz, because the SMA503 is not rated for those bands either. Shortwave and MW band performance is much BETTER with the MH-209 than with the SMA503, which seems counterintuitive unless you consider that the feedpoint method of the SMA503 may be presenting a very bad impedance far from the desired bands. FM broadcast was a little worse, but very usable. 800MHz seemed a little worse too.
Basically, I can access the local repeaters about as well as before, but I have to run say 1 to 2 Watts where I might only have needed 1/2 Watt before. The antenna is very flexible and seems like it won’t be prone to the breakage and kinking the SMA503 is known for. I would recommend the MH-209 antenna to people where range is not the overriding concern, but who need small size while maintaining adequate performance.
intermittent receive audio on internal speaker
The Yaesu VX-7, while overall an excellent amateur transceiver, suffers from a problem it shares with certain commercial handheld radios, that is of losing receive audio intermittently. The loss of audio stems from the flexible tensioned metal tangs that make contact to tin patches on the VX-7 internal speaker. I bent the speaker tension tangs outward resulting in about 1.5 mm more outward protrusion, thus reenacting a secure connection to the internal speaker.
Overbending these tangs could cause them to break, or worse, weaken them so they break later, shorting out internal components of the VX-7. I recommend you take this radio to a qualified repairperson to perform this repair.
It appears the VX-7 speaker model number is “Pryme 32N-A9906”; 8 Ω, 0.5 W