EXHIBIT 10.4
                                                                    ------------
                                 PROMISSORY NOTE
                                 ---------------

$3,500,000.00                                                 Freeport, Bahamas
                                                                  March 8, 1997

         FOR VALUE  RECEIVED,  STEVEN E.  BERNSTEIN,  an  individual  ("Maker"),
hereby promises to pay SBA  COMMUNICATIONS  CORPORATION,  a Florida  corporation
("Payee") the  principal  sum of Three Million Five Hundred  Thousand and 00/100
Dollars ($3,500,000.00),  together with accrued interest thereon at the Interest
Rate (as defined below).

         The principal amount payable under this Note, together with all accrued
interest thereon,  shall be paid in full on the date (the "Maturity Date") which
is the  earlier  to occur of (a) March 8,  2000,  or (b) the date upon  which an
initial public offering of Payee's common stock is consummated.  Notwithstanding
anything  set  forth  herein  to  the  contrary,  Maker  may,  in  Maker's  sole
discretion,  elect to pay Payee all principal and interest due and payable under
this Note on the Maturity  Date either in (i) lawful money of the United  States
of America,  or (ii) common stock of Payee valued at the initial public offering
price per share. It is understood and agreed that no principal or interest under
this Note shall be payable until the Maturity Date.

         For  purposes  of this Note,  the term  "Interest  Rate"  shall mean an
annual  interest  rate  at all  times  equal  to  the  applicable  federal  rate
determined from time to time by the Internal Revenue Service.  Interest shall be
computed  on the basis of a three  hundred  sixty  (360) day year for the actual
number of days elapsed.

         If Maker shall fail to pay any  principal  or interest  due  hereunder,
then Payee shall be entitled to exercise any right or remedy  available to Payee
under the Security Agreement (as defined below), at law or in equity.

         This  Note  is  secured  by the  Pledge  and  Security  Agreement  (the
"Security  Agreement"),  dated as of the date hereof,  between Maker, as debtor,
and Payee,  as secured  party.  The terms of the Security  Agreement  are hereby
incorporated by this reference and shall be deemed to be a part of this Note.

         Maker may prepay  this Note,  in whole or in part,  upon prior  written
notice to Payee,  without premium or penalty,  so long as Maker pays all accrued
interest unpaid under this Note with respect to the amount prepaid.

         This Note shall be governed by and  construed  in  accordance  with the
internal laws of the State of Florida, without regard to principles of conflicts
of law.

         This  Note may not be  changed  or  terminated  orally,  but only by an
agreement in writing signed by the party against whom enforcement of such change
or termination is sought.

 
         The terms and  provisions of this Note are  severable.  In the event of
the  unenforceability or invalidity of any one or more of the terms,  covenants,
conditions or provisions of this Note under federal,  state or other  applicable
law,  such  unenforceability  or  invalidity  shall not render  any other  term,
covenant, condition or provision hereunder unenforceable or invalid.

         THIS NOTE IS WITHOUT ANY  RECOURSE  WHATSOEVER  AGAINST  MAKER.  IN ANY
ACTION BROUGHT TO ENFORCE THE  OBLIGATIONS OF MAKER UNDER THIS NOTE OR UNDER THE
SECURITY  AGREEMENT,  THE JUDGMENT OR DECREE SHALL BE ENFORCEABLE  AGAINST MAKER
ONLY TO THE EXTENT OF MAKER'S  INTEREST IN THE  "COLLATERAL"  (AS DEFINED IN THE
SECURITY  AGREEMENT),  AND ANY SUCH  JUDGMENT OR DECREE  SHALL NOT BE SUBJECT TO
EXECUTION ON, OR BE A LIEN ON ASSETS OF, MAKER (OTHER THAN MAKER'S  INTERESTS IN
THE  COLLATERAL).  IN NO EVENT SHALL PAYEE SEEK OR OBTAIN A DEFICIENCY  OR OTHER
MONEY JUDGMENT AGAINST MAKER.

         THIS  NOTE has been  executed  by Maker as of the date  first set forth
above.


                                            /s/ Steven E. Bernstein
                                        -------------------------------
                                             STEVEN E. BERNSTEIN




COMMONWEALTH    )
                ) SS:
OF THE BAHAMAS  )

         The foregoing instrument was sworn to, subscribed and acknowledged
before  me this 8th day of March, 1997, by Steven E. Bernstein,  |_| who is
personally  known  to  me  or  |x|  who has produced passport # 92419425 as
identification and who did take an oath.



                                      Print Name:  Rev. Dr. Wellington Pinder
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                                      Commission Number:
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                                      Commission Expires:
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                                                               (NOTARIAL SEAL)




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