Trying to solve this other cipher using the tools in the 'Black Chamber' from Simon Singh:http://www.simonsingh.net/The_Black_Chamber/substitutioncrackingtool.html
Paste the ciphertext into the bottom box and then start putting in your substitutions on the left to see the plaintext fill out in the top box.
For completeness - the ciphertext is:
LFGXVGV POH QTZGN JTILRWGX VHKXI DBCF HKITROL ZH HIRXXTTB TA
The 'vowel trowel' tool on there suggests that the five most likely vowels are T, X, R, G, I with freqs of 9, 7, 6, 6, 6 respectively. Which causes some issues with the word 'HIRXXTTB' as has been mentioned already.
However, frequency analysis of letters in such a short phrase will always be fraught with error.
The clearest candidate for a vowel is obviously T, with 9 occurrences, but with the possibility that at least one of the words might be a system name (and therefore potentially an obscure word), it could equally be anything!
All this supposes it is a straight substitution cipher where a ciphertext letter is always equals to the same key letter or:
C[sub]L[/sub]=K[sub]L'[/sub] for all L where A<=L<=Z
Which, if it's a keyed cipher, such as keyed Vigenère, would not be the case.
Following on from earlier posts, and above - that 'HIRXXTTB' limits things for a substitution cipher greatly - if it's a word. 'XXTT' = 'OONN', 'OOLL' are most likely, perhaps.
But, again - if it's a system name - then it could be anything.
Anyway, that's me for the moment.
Another possible wrinkle is that the Morse may be reversed, either completely or line by line.