The following folks have registered for the 29th Four Days In May event (2025).

Banquet, Symposium,  Zoom or Book Only

If you are not on this list and you have PAID.  Send an email to This email address is being protected from spambots. You need JavaScript enabled to view it. and we will get it straightened out. Include when you paid, how much you paid, and how you paid. If you have your Paypal receipt or Paypal transaction code, send that as well.  This list is current through the morning of 04/12/2025

We have been informed by the Holiday Inn that the FDIM block of rooms have sold out. We recommend that anyone wishing to stay at the Holiday in for FDIM to check with them periodically in the chance there may be a cancellation that might free up a room.  

Announcing - the 29th FDIM 2025 "LOGIC IC TRANSMITTER POWER CHALLENGE!"

It was common in the early days of solid-state QRP to rig up a 7400 TTL chip as a crude QRP transmitter.  With a crystal and a handful of parts, it was possible to put a few hundred milliwatts on the air for a couple bucks.   While these simple IC-based transmit circuits have fallen out of favor, QRPARCI is revisiting this bit of QRP history with the FDIM2025 LOGIC IC TRANSMITTER POWER CHALLENGE!  The challenge is simple:  Design and demonstrate a crystal-controlled 40M oscillator/PA to make the highest sustained power for a period of one minute using only a single 4000-series or 7400-series logic IC.  This event will take place at 8:00 PM Friday, May 16 during FDIM, and the winner recognized at the QRPARCI Banquet on Saturday, May 17, 2025.

The rules for the competition are simple, but we have to list every nit-picky detail to test your endurance anyway:  The design is to utilize a single 4000 or 7400 series logic IC as the only active circuit element.  There are no limits on the number of diodes, inductors, resistors, capacitors, or transformers, but a single IC may be the only active device.

The PA must be crystal controlled within the 40M amateur band.  One (or more) section of the IC must be a crystal oscillator to control the frequency of the transmitter and builders are encouraged to use their own crystals, though there will be 7030 kHz HC-49 crystals available at the competition. No external frequency source may be used.

ICs to be used must be of the 4000-series or 7400-series.  Different logic families of this type such as 74LSxx, 74HCxx, 54HCTxx etc. may be used.

The circuit must fit inside a 12” x 12” x 12” volume.  During the power test, the judges will cover the circuit with a blast shield to protect judges and contestants from flying bits!

All circuit components are to be visible for inspection.

A schematic of the circuit is to be provided with each entry.

A zero-to-24v variable power supply, 40M band-pass filter, dummy load and power meter will be supplied by the judges.

The competition will have two rounds of trials to demonstrate power output of each circuit, with the best performance of each circuit being its final score.  During each test, the builder will connect his circuit, set the power supply voltage and then announce to the judges when to begin measurement.  During a period of one minute in which the builder may not touch the circuit or power supply, the RF power output at the end of one minute will be taken as the score for that trial.  Failure of the circuit in that one minute test period results in a score of ZERO for that round!  

The winner is the circuit generating the highest power score during either of his two rounds. If the circuit fails during the first test period, the builder will have five minutes in which to repair it before the second round trials. If your entry sets off the smoke detector in the Holiday Inn, you will be disqualified and may be subjected to rude laughter and finger pointing during the rest of FDIM!

The winner of the FDIM2025 LOGIC IC TRANSMITTER POWER CHALLENGE! will be recognized at the QRPARCI Banquet Saturday May 17, 2025.

Questions regarding the POWER CHALLENGE may be addressed to David Cripe NM0S, This email address is being protected from spambots. You need JavaScript enabled to view it..  Good luck and good building!

All times are Eastern Daylight Time (UTC -4)

Wednesday May 14 - Registration from 7:30PM to 9:30PM 

Thursday May 15 - Registration starts at 7:30AM Outside the Ballroom

Make sure you pick up your FDIM badge from the registration table

Thursday May 15 - Seminars

Beginning at 8AM and breaking at 10:45AM

Restarting at 11:00AM 

Lunch is from Noon to 1:00PM - Lunch will be provided by QRP-ARCI

Restarting at 1:00PM and ending at 5:00PM

7PM to 8PM - Vendor registration and setup - Main Ballroom, no public access

8PM to 10PM - Vendor Night

Friday May 16th

Afternoon - W1REX Buildathon! 

7PM to 8PM - Club Registration and setup in the Main Ballroom, no public access

7PM to 8PM - Show and Tell Homebrew Contest Registration and setup in Ballroom

8PM to 9PM - Homebrew Contest Judging in the Ballroom

8PM to 10PM - IC Transmitter Challenge!

8PM to 10PM - Radio Show and Tell in the Ballroom

8PM to 10PM - Club Night in the Ballroom - The Michigan QRP Club will be hosting a Michigan Mity Mite Revival!

Saturday May 17th 

7PM - Awards Ceremony and Grand Banquet in Ballroom 

9PM - Post Banquet Chat Sessions, bring your QSL cards to trade

Sunday May 18th 

Hamvention and head back home

If you have any questions please let us know !

The 29th Four Days In May (FDIM) 2025 - the biggest and best QRP event in the World !

You can register at the event on Wednesday night May 14, and Thursday Morning May 15 before the symposium. 

FDIM will be held at the same location as last year,

We have been informed by the Holiday Inn that the FDIM block of rooms have now sold out. We recommend that anyone wishing to stay at the Holiday in for FDIM to check with them periodically in the chance there may be a cancellation that might free up a room.

FDIM is - MAY 15 - May 18 2025

REGISTRATIONS FOR FDIM WILL CLOSE ON APRIL 25 - PLEASE Register before April 25

Below is the pricing for 2025 FDIM - SAME as last year! 

Banquet - $40.00 per person

Symposium with Proceedings Book  - $35.00 per person  (Includes Lunch)

Proceedings Book - $15.00 per book

Zoom Only Link - $12.00 per person - Zoom Link will be emailed to you a few days before FDIM

Send your payment via paypal to  This email address is being protected from spambots. You need JavaScript enabled to view it. - Please list what you are buying in the comments of the order. 

INCLUDE THE CALL SIGN YOU WANT ON YOUR NAME TAG

Door prizes!!  

FDIM has some of the most generous prize donors of any event.  We have some MAJOR door prizes again this year! 

Elecraft test gear, CWMorse, Hannes Hiller, K6ARK Portable Radio, 3rd Planet Solar, Etherkits, Iowa QRP Club, QRP Labs,
Hamgadgets, DX Engineering donating a IC-705, Mindybear Surplus, Coffee and Ham Radios, Halibut Electronics, Begali Key,
4 States QRP Group, Sierra Radio Systems, Radioddity, Panther Creek Solutions - SPOOLTENNA, Hong's Electronics, 
QRP Builder, QRP Works, QRPme, Grayson Evans, HF Signals  plus many more! 

Prizes will be drawn both Thursday during the Forum, and Saturday evening during the Banquet.  

Stay tuned for more updates

Friday 16 May 2025
8PM to 10PM

FDIM 2025 - Homebrew Contest - Show and Tell

As in the past, we intend to allow entries in the Homebrew Contest to be displayed in the Ballroom on Club Night, Friday night, May 16, between 8PM and 10 PM. To enter an item in the contest and insure that it is part of the voting (on Friday night), you must register your item on Friday night between 7 PM and 8 PM. A registration table will be outside the main Ballroom at that time on both nights.

Read More:

Vendor Night
Thursday 15 May 2025 - 8PM - 10PM in the Ballroom
Vendor Night is free of charge !

Club Night  
Friday 16 May 2025 - 8PM to 10PM in the Ballroom 
Michigan QRP Club will be hosting the Michigan Mity Mite Challenge! 

Vendors and QRP clubs from around the World will be selling kits, components, antennas and all kinds of goodies.

This is a great place to buy. The vendors have time to chat and you can take your purchases back to the hotel room. For customers, doors open at 8.00pm

Vendors at FDIM have included -

• Brad Thompson, AA1IP
• Elecraft
• Dan Romanchik, KB6NU
• DX Engineering
• Four State QRP Group (4SQRP)
• Kanga UK
• Kanga USA
• LNR Precision
• Pro Audio Engineering
• QRPme

Book a Table

2025 is our 29th FDIM! 

Visiting FDIM for the first time ?

Here's a guide so you know what to expect . . .

More about :

The 2024 FDIM is now in the record books, what a great turnout, we hope you all had a great time.