The personal website of Scott W Harden

Improved MEPT Enclosure

I've been pretty busy lately, but I drip to the hardware store with the XYL produced a PVC enclosure that looked perfect for my ongoing MEPT (manned experimental propagation transmitter) projects. I didn't want to buy it (it was a little pricey by my standards, at $6 USD, which is about the total cost of the transmitter!) but the wife convinced me and I'm glad she did! I intended it to replace the styrofoam enclosure I had been using, but I wasn't thinking clearly and drilled holes in the box and mounted screws through them. While electrically this is a wonderful way to add antenna connections, thermally it was a bad idea. The main point of the enclosure was to be temperature stable! Oh well. I put the whole thing in the Styrofoam and as a test, I'm leaving it outside tonight. I can't wait to see how it goes! Here are some photos of the project.

Update: Even when being housed outdoors when temperature fluctuations vary greatly between day and night, this MEPT is surprisingly stable! When I open the box, it's very warm inside, so I am thinking that the voltage regulators and the MOSTFETs of the PA are heating the device nicely. Here's a capture spanning about 2 hours. The vertical height of each "V" is about 10Hz, so I estimate that for this span of time, drift is <1Hz. However, I do believe that long term (day to day) frequency stability is still not optimal, but only time will tell.

Signal report: briefly, this is my signal in Alaska courtesy of KL7UK. My signal is the V-shaped one near the bottom:

Markdown source code last modified on January 18th, 2021
---
title: Improved MEPT Enclosure
date: 2010-11-14 20:22:38
tags: qrss, amateur radio, circuit
---

# Improved MEPT Enclosure

__I've been pretty busy lately__, but I drip to the hardware store with the XYL produced a PVC enclosure that looked perfect for my ongoing MEPT (manned experimental propagation transmitter) projects. I didn't want to buy it (it was a little pricey by my standards, at $6 USD, which is about the total cost of the transmitter!) but the wife convinced me and I'm glad she did!  I intended it to replace the styrofoam enclosure I had been using, but I wasn't thinking clearly and drilled holes in the box and mounted screws through them.  While electrically this is a wonderful way to add antenna connections, thermally it was a bad idea.  The main point of the enclosure was to be temperature stable! Oh well. I put the whole thing in the Styrofoam and as a test, I'm leaving it outside tonight. I can't wait to see how it goes!  Here are some photos of the project.

<div class="text-center img-border">

[![](IMG_4526_thumb.jpg)](IMG_4526.jpg)
[![](IMG_4534_thumb.jpg)](IMG_4534.jpg)
[![](IMG_4547_thumb.jpg)](IMG_4547.jpg)
[![](IMG_4548_thumb.jpg)](IMG_4548.jpg)

</div>

__Update:__ Even when being housed outdoors when temperature fluctuations vary greatly between day and night, this MEPT is surprisingly stable! When I open the box, it's very warm inside, so I am thinking that the voltage regulators and the MOSTFETs of the PA are heating the device nicely.  Here's a capture spanning about 2 hours. The vertical height of each "V" is about 10Hz, so I estimate that for this span of time, drift is <1Hz.  However, I do believe that long term (day to day) frequency stability is still not optimal, but only time will tell.

<div class="text-center img-border">

[![](qrss_stable_thumb.jpg)](qrss_stable.jpg)

</div>

__Signal report__: briefly, this is my signal in Alaska courtesy of KL7UK. My signal is the V-shaped one near the bottom: 

<div class="text-center img-border">

[![](KL7UK_alaska_thumb.jpg)](KL7UK_alaska.jpg)

</div>