- September 30, 2021 at 11:39 pm #118347C. C.Participant
Total posts : 3
Over the summer, between moving house and mostly avoiding humanity because of the pandemic, I built and experimented with a cheap 70mW Kit Transmitter from Thailand, and while it works fairly well as is (given it’s my first time building one), it’s on the quiet side, and is prone to distortion (in particular, bass and low mids tend to have a slightly gritty sound at almost any volume).
That being said, working within these shortcomings, I can make it sound good enough. However, I think I’m going to upgrade to a Talking House transmitter after I make a few documented modifications to improve sound quality, as I think it is a far superior unit.
In the meantime, I’m wondering if there’s any room for improvement in my kit transmitter (improving frequency response, increasing headroom, increasing power to the maximum 100mW, etc), as I don’t want to junk it. Not after all the work I put into it (I modified it with an on/off switch and power indicator, stereo phono jacks (summed to mono) for audio input, a BNC jack for RF output, and panel mounted volume potentiometer and put it all in an electronics project box).
Anyway, attached to this post is the “schematic”– it’s mostly just a fancy block diagram, but it’s enough to get an idea of how the circuit is laid out, I think.
Attachments:You must be logged in to view attached files.October 1, 2021 at 8:59 am #118349MarkModerator
Total posts : 665
I think your electronics knowledge is better than mine so I can’t really help you with the audio quality being not so good, or what to do to get to the 100mW into the final amp, but as for trying to get to the volume of the other stations you need two things. The transmitter has to be able to get to 100% modulation and you need some kind of limiting/compression between the source and the transmitter. Limiting is the most important. If you think of an analog VU meter with no limiting the needle jumps around with the sound dynamics. With limiting and some compression there’s much less movement of the needle and you can up the volume to just at the red line with only an occasional flicking into the red.
But the transmitter has to be capable of 100% modulation to not sound too quiet all the time. But I can’t advise you on what to do to your kit to do that….maybe someone here can?
I use this which is fantastic for processing…..https://www.schlockwood.com/products
As you saw there’s a few videos on improving the Talking House for better frequency response and modulation on the older models although if you do get one the new ones called i AM radio transmitter have been factory improved with the changes made from the older ones.
- This reply was modified 3 weeks, 1 day ago by Mark.
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