Evidently, earlier military HF radioteletype (RATT) transmitters were designed to produce mark high. Later military gear produces mark low. When and why did this change occur? It is a puzzlement to me that anyone would have created such confusion on purpose. Nets would have been a nightmare. <div dir="auto">Note- I am talking about the RF frequency being low or high. </div><div dir="auto">Cheers</div><div dir="auto">Nick</div>-- <br><div dir="ltr" class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr">Nick England K4NYW<br><a href="http://www.navy-radio.com" target="_blank">www.navy-radio.com</a><br></div></div></div></div></div></div>